(function(f) {
    if (typeof exports === "object" && typeof module !== "undefined") {
        module.exports = f()
    } else if (typeof define === "function" && define.amd) {
        define([], f)
    } else {
        var g;
        if (typeof window !== "undefined") {
            g = window
        } else if (typeof global !== "undefined") {
            g = global
        } else if (typeof self !== "undefined") {
            g = self
        } else {
            g = this
        }
        g.adapter = f()
    }
})(function() {
    var define, module, exports;
    return (function e(t, n, r) {
        function s(o, u) {
            if (!n[o]) {
                if (!t[o]) {
                    var a = typeof require == "function" && require;
                    if (!u && a) return a(o, !0);
                    if (i) return i(o, !0);
                    var f = new Error("Cannot find module '" + o + "'");
                    throw f.code = "MODULE_NOT_FOUND", f
                }
                var l = n[o] = {
                    exports: {}
                };
                t[o][0].call(l.exports, function(e) {
                    var n = t[o][1][e];
                    return s(n ? n : e)
                }, l, l.exports, e, t, n, r)
            }
            return n[o].exports
        }
        var i = typeof require == "function" && require;
        for (var o = 0; o < r.length; o++) s(r[o]);
        return s
    })({
        1: [function(require, module, exports) {
            /*
             *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            var SDPUtils = require('sdp');

            function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
                var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

                // Map ICE parameters (ufrag, pwd) to SDP.
                sdp += SDPUtils.writeIceParameters(
                    transceiver.iceGatherer.getLocalParameters());

                // Map DTLS parameters to SDP.
                sdp += SDPUtils.writeDtlsParameters(
                    transceiver.dtlsTransport.getLocalParameters(),
                    type === 'offer' ? 'actpass' : dtlsRole || 'active');

                sdp += 'a=mid:' + transceiver.mid + '\r\n';

                if (transceiver.rtpSender && transceiver.rtpReceiver) {
                    sdp += 'a=sendrecv\r\n';
                } else if (transceiver.rtpSender) {
                    sdp += 'a=sendonly\r\n';
                } else if (transceiver.rtpReceiver) {
                    sdp += 'a=recvonly\r\n';
                } else {
                    sdp += 'a=inactive\r\n';
                }

                if (transceiver.rtpSender) {
                    var trackId = transceiver.rtpSender._initialTrackId ||
                        transceiver.rtpSender.track.id;
                    transceiver.rtpSender._initialTrackId = trackId;
                    // spec.
                    var msid = 'msid:' + (stream ? stream.id : '-') + ' ' +
                        trackId + '\r\n';
                    sdp += 'a=' + msid;
                    // for Chrome. Legacy should no longer be required.
                    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                        ' ' + msid;

                    // RTX
                    if (transceiver.sendEncodingParameters[0].rtx) {
                        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                            ' ' + msid;
                        sdp += 'a=ssrc-group:FID ' +
                            transceiver.sendEncodingParameters[0].ssrc + ' ' +
                            transceiver.sendEncodingParameters[0].rtx.ssrc +
                            '\r\n';
                    }
                }
                // FIXME: this should be written by writeRtpDescription.
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                    ' cname:' + SDPUtils.localCName + '\r\n';
                if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
                    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                        ' cname:' + SDPUtils.localCName + '\r\n';
                }
                return sdp;
            }

            // Edge does not like
            // 1) stun: filtered after 14393 unless ?transport=udp is present
            // 2) turn: that does not have all of turn:host:port?transport=udp
            // 3) turn: with ipv6 addresses
            // 4) turn: occurring muliple times
            function filterIceServers(iceServers, edgeVersion) {
                var hasTurn = false;
                iceServers = JSON.parse(JSON.stringify(iceServers));
                return iceServers.filter(function(server) {
                    if (server && (server.urls || server.url)) {
                        var urls = server.urls || server.url;
                        if (server.url && !server.urls) {
                            console.warn('RTCIceServer.url is deprecated! Use urls instead.');
                        }
                        var isString = typeof urls === 'string';
                        if (isString) {
                            urls = [urls];
                        }
                        urls = urls.filter(function(url) {
                            var validTurn = url.indexOf('turn:') === 0 &&
                                url.indexOf('transport=udp') !== -1 &&
                                url.indexOf('turn:[') === -1 &&
                                !hasTurn;

                            if (validTurn) {
                                hasTurn = true;
                                return true;
                            }
                            return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
                                url.indexOf('?transport=udp') === -1;
                        });

                        delete server.url;
                        server.urls = isString ? urls[0] : urls;
                        return !!urls.length;
                    }
                });
            }

            // Determines the intersection of local and remote capabilities.
            function getCommonCapabilities(localCapabilities, remoteCapabilities) {
                var commonCapabilities = {
                    codecs: [],
                    headerExtensions: [],
                    fecMechanisms: []
                };

                var findCodecByPayloadType = function(pt, codecs) {
                    pt = parseInt(pt, 10);
                    for (var i = 0; i < codecs.length; i++) {
                        if (codecs[i].payloadType === pt ||
                            codecs[i].preferredPayloadType === pt) {
                            return codecs[i];
                        }
                    }
                };

                var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
                    var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs);
                    var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs);
                    return lCodec && rCodec &&
                        lCodec.name.toLowerCase() === rCodec.name.toLowerCase();
                };

                localCapabilities.codecs.forEach(function(lCodec) {
                    for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
                        var rCodec = remoteCapabilities.codecs[i];
                        if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
                            lCodec.clockRate === rCodec.clockRate) {
                            if (lCodec.name.toLowerCase() === 'rtx' &&
                                lCodec.parameters && rCodec.parameters.apt) {
                                // for RTX we need to find the local rtx that has a apt
                                // which points to the same local codec as the remote one.
                                if (!rtxCapabilityMatches(lCodec, rCodec,
                                        localCapabilities.codecs, remoteCapabilities.codecs)) {
                                    continue;
                                }
                            }
                            rCodec = JSON.parse(JSON.stringify(rCodec)); // deepcopy
                            // number of channels is the highest common number of channels
                            rCodec.numChannels = Math.min(lCodec.numChannels,
                                rCodec.numChannels);
                            // push rCodec so we reply with offerer payload type
                            commonCapabilities.codecs.push(rCodec);

                            // determine common feedback mechanisms
                            rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
                                for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
                                    if (lCodec.rtcpFeedback[j].type === fb.type &&
                                        lCodec.rtcpFeedback[j].parameter === fb.parameter) {
                                        return true;
                                    }
                                }
                                return false;
                            });
                            // FIXME: also need to determine .parameters
                            //  see https://github.com/openpeer/ortc/issues/569
                            break;
                        }
                    }
                });

                localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
                    for (var i = 0; i < remoteCapabilities.headerExtensions.length; i++) {
                        var rHeaderExtension = remoteCapabilities.headerExtensions[i];
                        if (lHeaderExtension.uri === rHeaderExtension.uri) {
                            commonCapabilities.headerExtensions.push(rHeaderExtension);
                            break;
                        }
                    }
                });

                // FIXME: fecMechanisms
                return commonCapabilities;
            }

            // is action=setLocalDescription with type allowed in signalingState
            function isActionAllowedInSignalingState(action, type, signalingState) {
                return {
                    offer: {
                        setLocalDescription: ['stable', 'have-local-offer'],
                        setRemoteDescription: ['stable', 'have-remote-offer']
                    },
                    answer: {
                        setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
                        setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
                    }
                }[type][action].indexOf(signalingState) !== -1;
            }

            function maybeAddCandidate(iceTransport, candidate) {
                // Edge's internal representation adds some fields therefore
                // not all fieldѕ are taken into account.
                var alreadyAdded = iceTransport.getRemoteCandidates()
                    .find(function(remoteCandidate) {
                        return candidate.foundation === remoteCandidate.foundation &&
                            candidate.ip === remoteCandidate.ip &&
                            candidate.port === remoteCandidate.port &&
                            candidate.priority === remoteCandidate.priority &&
                            candidate.protocol === remoteCandidate.protocol &&
                            candidate.type === remoteCandidate.type;
                    });
                if (!alreadyAdded) {
                    iceTransport.addRemoteCandidate(candidate);
                }
                return !alreadyAdded;
            }


            function makeError(name, description) {
                var e = new Error(description);
                e.name = name;
                // legacy error codes from https://heycam.github.io/webidl/#idl-DOMException-error-names
                e.code = {
                    NotSupportedError: 9,
                    InvalidStateError: 11,
                    InvalidAccessError: 15,
                    TypeError: undefined,
                    OperationError: undefined
                }[name];
                return e;
            }

            module.exports = function(window, edgeVersion) {
                // https://w3c.github.io/mediacapture-main/#mediastream
                // Helper function to add the track to the stream and
                // dispatch the event ourselves.
                function addTrackToStreamAndFireEvent(track, stream) {
                    stream.addTrack(track);
                    stream.dispatchEvent(new window.MediaStreamTrackEvent('addtrack', {
                        track: track
                    }));
                }

                function removeTrackFromStreamAndFireEvent(track, stream) {
                    stream.removeTrack(track);
                    stream.dispatchEvent(new window.MediaStreamTrackEvent('removetrack', {
                        track: track
                    }));
                }

                function fireAddTrack(pc, track, receiver, streams) {
                    var trackEvent = new Event('track');
                    trackEvent.track = track;
                    trackEvent.receiver = receiver;
                    trackEvent.transceiver = {
                        receiver: receiver
                    };
                    trackEvent.streams = streams;
                    window.setTimeout(function() {
                        pc._dispatchEvent('track', trackEvent);
                    });
                }

                var RTCPeerConnection = function(config) {
                    var pc = this;

                    var _eventTarget = document.createDocumentFragment();
                    ['addEventListener', 'removeEventListener', 'dispatchEvent']
                    .forEach(function(method) {
                        pc[method] = _eventTarget[method].bind(_eventTarget);
                    });

                    this.canTrickleIceCandidates = null;

                    this.needNegotiation = false;

                    this.localStreams = [];
                    this.remoteStreams = [];

                    this.localDescription = null;
                    this.remoteDescription = null;

                    this.signalingState = 'stable';
                    this.iceConnectionState = 'new';
                    this.connectionState = 'new';
                    this.iceGatheringState = 'new';

                    config = JSON.parse(JSON.stringify(config || {}));

                    this.usingBundle = config.bundlePolicy === 'max-bundle';
                    if (config.rtcpMuxPolicy === 'negotiate') {
                        throw (makeError('NotSupportedError',
                            'rtcpMuxPolicy \'negotiate\' is not supported'));
                    } else if (!config.rtcpMuxPolicy) {
                        config.rtcpMuxPolicy = 'require';
                    }

                    switch (config.iceTransportPolicy) {
                        case 'all':
                        case 'relay':
                            break;
                        default:
                            config.iceTransportPolicy = 'all';
                            break;
                    }

                    switch (config.bundlePolicy) {
                        case 'balanced':
                        case 'max-compat':
                        case 'max-bundle':
                            break;
                        default:
                            config.bundlePolicy = 'balanced';
                            break;
                    }

                    config.iceServers = filterIceServers(config.iceServers || [], edgeVersion);

                    this._iceGatherers = [];
                    if (config.iceCandidatePoolSize) {
                        for (var i = config.iceCandidatePoolSize; i > 0; i--) {
                            this._iceGatherers.push(new window.RTCIceGatherer({
                                iceServers: config.iceServers,
                                gatherPolicy: config.iceTransportPolicy
                            }));
                        }
                    } else {
                        config.iceCandidatePoolSize = 0;
                    }

                    this._config = config;

                    // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
                    // everything that is needed to describe a SDP m-line.
                    this.transceivers = [];

                    this._sdpSessionId = SDPUtils.generateSessionId();
                    this._sdpSessionVersion = 0;

                    this._dtlsRole = undefined; // role for a=setup to use in answers.

                    this._isClosed = false;
                };

                // set up event handlers on prototype
                RTCPeerConnection.prototype.onicecandidate = null;
                RTCPeerConnection.prototype.onaddstream = null;
                RTCPeerConnection.prototype.ontrack = null;
                RTCPeerConnection.prototype.onremovestream = null;
                RTCPeerConnection.prototype.onsignalingstatechange = null;
                RTCPeerConnection.prototype.oniceconnectionstatechange = null;
                RTCPeerConnection.prototype.onconnectionstatechange = null;
                RTCPeerConnection.prototype.onicegatheringstatechange = null;
                RTCPeerConnection.prototype.onnegotiationneeded = null;
                RTCPeerConnection.prototype.ondatachannel = null;

                RTCPeerConnection.prototype._dispatchEvent = function(name, event) {
                    if (this._isClosed) {
                        return;
                    }
                    this.dispatchEvent(event);
                    if (typeof this['on' + name] === 'function') {
                        this['on' + name](event);
                    }
                };

                RTCPeerConnection.prototype._emitGatheringStateChange = function() {
                    var event = new Event('icegatheringstatechange');
                    this._dispatchEvent('icegatheringstatechange', event);
                };

                RTCPeerConnection.prototype.getConfiguration = function() {
                    return this._config;
                };

                RTCPeerConnection.prototype.getLocalStreams = function() {
                    return this.localStreams;
                };

                RTCPeerConnection.prototype.getRemoteStreams = function() {
                    return this.remoteStreams;
                };

                // internal helper to create a transceiver object.
                // (which is not yet the same as the WebRTC 1.0 transceiver)
                RTCPeerConnection.prototype._createTransceiver = function(kind, doNotAdd) {
                    var hasBundleTransport = this.transceivers.length > 0;
                    var transceiver = {
                        track: null,
                        iceGatherer: null,
                        iceTransport: null,
                        dtlsTransport: null,
                        localCapabilities: null,
                        remoteCapabilities: null,
                        rtpSender: null,
                        rtpReceiver: null,
                        kind: kind,
                        mid: null,
                        sendEncodingParameters: null,
                        recvEncodingParameters: null,
                        stream: null,
                        associatedRemoteMediaStreams: [],
                        wantReceive: true
                    };
                    if (this.usingBundle && hasBundleTransport) {
                        transceiver.iceTransport = this.transceivers[0].iceTransport;
                        transceiver.dtlsTransport = this.transceivers[0].dtlsTransport;
                    } else {
                        var transports = this._createIceAndDtlsTransports();
                        transceiver.iceTransport = transports.iceTransport;
                        transceiver.dtlsTransport = transports.dtlsTransport;
                    }
                    if (!doNotAdd) {
                        this.transceivers.push(transceiver);
                    }
                    return transceiver;
                };

                RTCPeerConnection.prototype.addTrack = function(track, stream) {
                    if (this._isClosed) {
                        throw makeError('InvalidStateError',
                            'Attempted to call addTrack on a closed peerconnection.');
                    }

                    var alreadyExists = this.transceivers.find(function(s) {
                        return s.track === track;
                    });

                    if (alreadyExists) {
                        throw makeError('InvalidAccessError', 'Track already exists.');
                    }

                    var transceiver;
                    for (var i = 0; i < this.transceivers.length; i++) {
                        if (!this.transceivers[i].track &&
                            this.transceivers[i].kind === track.kind) {
                            transceiver = this.transceivers[i];
                        }
                    }
                    if (!transceiver) {
                        transceiver = this._createTransceiver(track.kind);
                    }

                    this._maybeFireNegotiationNeeded();

                    if (this.localStreams.indexOf(stream) === -1) {
                        this.localStreams.push(stream);
                    }

                    transceiver.track = track;
                    transceiver.stream = stream;
                    transceiver.rtpSender = new window.RTCRtpSender(track,
                        transceiver.dtlsTransport);
                    return transceiver.rtpSender;
                };

                RTCPeerConnection.prototype.addStream = function(stream) {
                    var pc = this;
                    if (edgeVersion >= 15025) {
                        stream.getTracks().forEach(function(track) {
                            pc.addTrack(track, stream);
                        });
                    } else {
                        // Clone is necessary for local demos mostly, attaching directly
                        // to two different senders does not work (build 10547).
                        // Fixed in 15025 (or earlier)
                        var clonedStream = stream.clone();
                        stream.getTracks().forEach(function(track, idx) {
                            var clonedTrack = clonedStream.getTracks()[idx];
                            track.addEventListener('enabled', function(event) {
                                clonedTrack.enabled = event.enabled;
                            });
                        });
                        clonedStream.getTracks().forEach(function(track) {
                            pc.addTrack(track, clonedStream);
                        });
                    }
                };

                RTCPeerConnection.prototype.removeTrack = function(sender) {
                    if (this._isClosed) {
                        throw makeError('InvalidStateError',
                            'Attempted to call removeTrack on a closed peerconnection.');
                    }

                    if (!(sender instanceof window.RTCRtpSender)) {
                        throw new TypeError('Argument 1 of RTCPeerConnection.removeTrack ' +
                            'does not implement interface RTCRtpSender.');
                    }

                    var transceiver = this.transceivers.find(function(t) {
                        return t.rtpSender === sender;
                    });

                    if (!transceiver) {
                        throw makeError('InvalidAccessError',
                            'Sender was not created by this connection.');
                    }
                    var stream = transceiver.stream;

                    transceiver.rtpSender.stop();
                    transceiver.rtpSender = null;
                    transceiver.track = null;
                    transceiver.stream = null;

                    // remove the stream from the set of local streams
                    var localStreams = this.transceivers.map(function(t) {
                        return t.stream;
                    });
                    if (localStreams.indexOf(stream) === -1 &&
                        this.localStreams.indexOf(stream) > -1) {
                        this.localStreams.splice(this.localStreams.indexOf(stream), 1);
                    }

                    this._maybeFireNegotiationNeeded();
                };

                RTCPeerConnection.prototype.removeStream = function(stream) {
                    var pc = this;
                    stream.getTracks().forEach(function(track) {
                        var sender = pc.getSenders().find(function(s) {
                            return s.track === track;
                        });
                        if (sender) {
                            pc.removeTrack(sender);
                        }
                    });
                };

                RTCPeerConnection.prototype.getSenders = function() {
                    return this.transceivers.filter(function(transceiver) {
                            return !!transceiver.rtpSender;
                        })
                        .map(function(transceiver) {
                            return transceiver.rtpSender;
                        });
                };

                RTCPeerConnection.prototype.getReceivers = function() {
                    return this.transceivers.filter(function(transceiver) {
                            return !!transceiver.rtpReceiver;
                        })
                        .map(function(transceiver) {
                            return transceiver.rtpReceiver;
                        });
                };


                RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
                    usingBundle) {
                    var pc = this;
                    if (usingBundle && sdpMLineIndex > 0) {
                        return this.transceivers[0].iceGatherer;
                    } else if (this._iceGatherers.length) {
                        return this._iceGatherers.shift();
                    }
                    var iceGatherer = new window.RTCIceGatherer({
                        iceServers: this._config.iceServers,
                        gatherPolicy: this._config.iceTransportPolicy
                    });
                    Object.defineProperty(iceGatherer, 'state', {
                        value: 'new',
                        writable: true
                    });

                    this.transceivers[sdpMLineIndex].bufferedCandidateEvents = [];
                    this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
                        var end = !event.candidate || Object.keys(event.candidate).length === 0;
                        // polyfill since RTCIceGatherer.state is not implemented in
                        // Edge 10547 yet.
                        iceGatherer.state = end ? 'completed' : 'gathering';
                        if (pc.transceivers[sdpMLineIndex].bufferedCandidateEvents !== null) {
                            pc.transceivers[sdpMLineIndex].bufferedCandidateEvents.push(event);
                        }
                    };
                    iceGatherer.addEventListener('localcandidate',
                        this.transceivers[sdpMLineIndex].bufferCandidates);
                    return iceGatherer;
                };

                // start gathering from an RTCIceGatherer.
                RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
                    var pc = this;
                    var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
                    if (iceGatherer.onlocalcandidate) {
                        return;
                    }
                    var bufferedCandidateEvents =
                        this.transceivers[sdpMLineIndex].bufferedCandidateEvents;
                    this.transceivers[sdpMLineIndex].bufferedCandidateEvents = null;
                    iceGatherer.removeEventListener('localcandidate',
                        this.transceivers[sdpMLineIndex].bufferCandidates);
                    iceGatherer.onlocalcandidate = function(evt) {
                        if (pc.usingBundle && sdpMLineIndex > 0) {
                            // if we know that we use bundle we can drop candidates with
                            // ѕdpMLineIndex > 0. If we don't do this then our state gets
                            // confused since we dispose the extra ice gatherer.
                            return;
                        }
                        var event = new Event('icecandidate');
                        event.candidate = {
                            sdpMid: mid,
                            sdpMLineIndex: sdpMLineIndex
                        };

                        var cand = evt.candidate;
                        // Edge emits an empty object for RTCIceCandidateComplete‥
                        var end = !cand || Object.keys(cand).length === 0;
                        if (end) {
                            // polyfill since RTCIceGatherer.state is not implemented in
                            // Edge 10547 yet.
                            if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
                                iceGatherer.state = 'completed';
                            }
                        } else {
                            if (iceGatherer.state === 'new') {
                                iceGatherer.state = 'gathering';
                            }
                            // RTCIceCandidate doesn't have a component, needs to be added
                            cand.component = 1;
                            // also the usernameFragment. TODO: update SDP to take both variants.
                            cand.ufrag = iceGatherer.getLocalParameters().usernameFragment;

                            var serializedCandidate = SDPUtils.writeCandidate(cand);
                            event.candidate = Object.assign(event.candidate,
                                SDPUtils.parseCandidate(serializedCandidate));

                            event.candidate.candidate = serializedCandidate;
                            event.candidate.toJSON = function() {
                                return {
                                    candidate: event.candidate.candidate,
                                    sdpMid: event.candidate.sdpMid,
                                    sdpMLineIndex: event.candidate.sdpMLineIndex,
                                    usernameFragment: event.candidate.usernameFragment
                                };
                            };
                        }

                        // update local description.
                        var sections = SDPUtils.getMediaSections(pc.localDescription.sdp);
                        if (!end) {
                            sections[event.candidate.sdpMLineIndex] +=
                                'a=' + event.candidate.candidate + '\r\n';
                        } else {
                            sections[event.candidate.sdpMLineIndex] +=
                                'a=end-of-candidates\r\n';
                        }
                        pc.localDescription.sdp =
                            SDPUtils.getDescription(pc.localDescription.sdp) +
                            sections.join('');
                        var complete = pc.transceivers.every(function(transceiver) {
                            return transceiver.iceGatherer &&
                                transceiver.iceGatherer.state === 'completed';
                        });

                        if (pc.iceGatheringState !== 'gathering') {
                            pc.iceGatheringState = 'gathering';
                            pc._emitGatheringStateChange();
                        }

                        // Emit candidate. Also emit null candidate when all gatherers are
                        // complete.
                        if (!end) {
                            pc._dispatchEvent('icecandidate', event);
                        }
                        if (complete) {
                            pc._dispatchEvent('icecandidate', new Event('icecandidate'));
                            pc.iceGatheringState = 'complete';
                            pc._emitGatheringStateChange();
                        }
                    };

                    // emit already gathered candidates.
                    window.setTimeout(function() {
                        bufferedCandidateEvents.forEach(function(e) {
                            iceGatherer.onlocalcandidate(e);
                        });
                    }, 0);
                };

                // Create ICE transport and DTLS transport.
                RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
                    var pc = this;
                    var iceTransport = new window.RTCIceTransport(null);
                    iceTransport.onicestatechange = function() {
                        pc._updateIceConnectionState();
                        pc._updateConnectionState();
                    };

                    var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
                    dtlsTransport.ondtlsstatechange = function() {
                        pc._updateConnectionState();
                    };
                    dtlsTransport.onerror = function() {
                        // onerror does not set state to failed by itself.
                        Object.defineProperty(dtlsTransport, 'state', {
                            value: 'failed',
                            writable: true
                        });
                        pc._updateConnectionState();
                    };

                    return {
                        iceTransport: iceTransport,
                        dtlsTransport: dtlsTransport
                    };
                };

                // Destroy ICE gatherer, ICE transport and DTLS transport.
                // Without triggering the callbacks.
                RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
                    sdpMLineIndex) {
                    var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
                    if (iceGatherer) {
                        delete iceGatherer.onlocalcandidate;
                        delete this.transceivers[sdpMLineIndex].iceGatherer;
                    }
                    var iceTransport = this.transceivers[sdpMLineIndex].iceTransport;
                    if (iceTransport) {
                        delete iceTransport.onicestatechange;
                        delete this.transceivers[sdpMLineIndex].iceTransport;
                    }
                    var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport;
                    if (dtlsTransport) {
                        delete dtlsTransport.ondtlsstatechange;
                        delete dtlsTransport.onerror;
                        delete this.transceivers[sdpMLineIndex].dtlsTransport;
                    }
                };

                // Start the RTP Sender and Receiver for a transceiver.
                RTCPeerConnection.prototype._transceive = function(transceiver,
                    send, recv) {
                    var params = getCommonCapabilities(transceiver.localCapabilities,
                        transceiver.remoteCapabilities);
                    if (send && transceiver.rtpSender) {
                        params.encodings = transceiver.sendEncodingParameters;
                        params.rtcp = {
                            cname: SDPUtils.localCName,
                            compound: transceiver.rtcpParameters.compound
                        };
                        if (transceiver.recvEncodingParameters.length) {
                            params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
                        }
                        transceiver.rtpSender.send(params);
                    }
                    if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
                        // remove RTX field in Edge 14942
                        if (transceiver.kind === 'video' &&
                            transceiver.recvEncodingParameters &&
                            edgeVersion < 15019) {
                            transceiver.recvEncodingParameters.forEach(function(p) {
                                delete p.rtx;
                            });
                        }
                        if (transceiver.recvEncodingParameters.length) {
                            params.encodings = transceiver.recvEncodingParameters;
                        } else {
                            params.encodings = [{}];
                        }
                        params.rtcp = {
                            compound: transceiver.rtcpParameters.compound
                        };
                        if (transceiver.rtcpParameters.cname) {
                            params.rtcp.cname = transceiver.rtcpParameters.cname;
                        }
                        if (transceiver.sendEncodingParameters.length) {
                            params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
                        }
                        transceiver.rtpReceiver.receive(params);
                    }
                };

                RTCPeerConnection.prototype.setLocalDescription = function(description) {
                    var pc = this;

                    // Note: pranswer is not supported.
                    if (['offer', 'answer'].indexOf(description.type) === -1) {
                        return Promise.reject(makeError('TypeError',
                            'Unsupported type "' + description.type + '"'));
                    }

                    if (!isActionAllowedInSignalingState('setLocalDescription',
                            description.type, pc.signalingState) || pc._isClosed) {
                        return Promise.reject(makeError('InvalidStateError',
                            'Can not set local ' + description.type +
                            ' in state ' + pc.signalingState));
                    }

                    var sections;
                    var sessionpart;
                    if (description.type === 'offer') {
                        // VERY limited support for SDP munging. Limited to:
                        // * changing the order of codecs
                        sections = SDPUtils.splitSections(description.sdp);
                        sessionpart = sections.shift();
                        sections.forEach(function(mediaSection, sdpMLineIndex) {
                            var caps = SDPUtils.parseRtpParameters(mediaSection);
                            pc.transceivers[sdpMLineIndex].localCapabilities = caps;
                        });

                        pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                            pc._gather(transceiver.mid, sdpMLineIndex);
                        });
                    } else if (description.type === 'answer') {
                        sections = SDPUtils.splitSections(pc.remoteDescription.sdp);
                        sessionpart = sections.shift();
                        var isIceLite = SDPUtils.matchPrefix(sessionpart,
                            'a=ice-lite').length > 0;
                        sections.forEach(function(mediaSection, sdpMLineIndex) {
                            var transceiver = pc.transceivers[sdpMLineIndex];
                            var iceGatherer = transceiver.iceGatherer;
                            var iceTransport = transceiver.iceTransport;
                            var dtlsTransport = transceiver.dtlsTransport;
                            var localCapabilities = transceiver.localCapabilities;
                            var remoteCapabilities = transceiver.remoteCapabilities;

                            // treat bundle-only as not-rejected.
                            var rejected = SDPUtils.isRejected(mediaSection) &&
                                SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;

                            if (!rejected && !transceiver.rejected) {
                                var remoteIceParameters = SDPUtils.getIceParameters(
                                    mediaSection, sessionpart);
                                var remoteDtlsParameters = SDPUtils.getDtlsParameters(
                                    mediaSection, sessionpart);
                                if (isIceLite) {
                                    remoteDtlsParameters.role = 'server';
                                }

                                if (!pc.usingBundle || sdpMLineIndex === 0) {
                                    pc._gather(transceiver.mid, sdpMLineIndex);
                                    if (iceTransport.state === 'new') {
                                        iceTransport.start(iceGatherer, remoteIceParameters,
                                            isIceLite ? 'controlling' : 'controlled');
                                    }
                                    if (dtlsTransport.state === 'new') {
                                        dtlsTransport.start(remoteDtlsParameters);
                                    }
                                }

                                // Calculate intersection of capabilities.
                                var params = getCommonCapabilities(localCapabilities,
                                    remoteCapabilities);

                                // Start the RTCRtpSender. The RTCRtpReceiver for this
                                // transceiver has already been started in setRemoteDescription.
                                pc._transceive(transceiver,
                                    params.codecs.length > 0,
                                    false);
                            }
                        });
                    }

                    pc.localDescription = {
                        type: description.type,
                        sdp: description.sdp
                    };
                    if (description.type === 'offer') {
                        pc._updateSignalingState('have-local-offer');
                    } else {
                        pc._updateSignalingState('stable');
                    }

                    return Promise.resolve();
                };

                RTCPeerConnection.prototype.setRemoteDescription = function(description) {
                    var pc = this;

                    // Note: pranswer is not supported.
                    if (['offer', 'answer'].indexOf(description.type) === -1) {
                        return Promise.reject(makeError('TypeError',
                            'Unsupported type "' + description.type + '"'));
                    }

                    if (!isActionAllowedInSignalingState('setRemoteDescription',
                            description.type, pc.signalingState) || pc._isClosed) {
                        return Promise.reject(makeError('InvalidStateError',
                            'Can not set remote ' + description.type +
                            ' in state ' + pc.signalingState));
                    }

                    var streams = {};
                    pc.remoteStreams.forEach(function(stream) {
                        streams[stream.id] = stream;
                    });
                    var receiverList = [];
                    var sections = SDPUtils.splitSections(description.sdp);
                    var sessionpart = sections.shift();
                    var isIceLite = SDPUtils.matchPrefix(sessionpart,
                        'a=ice-lite').length > 0;
                    var usingBundle = SDPUtils.matchPrefix(sessionpart,
                        'a=group:BUNDLE ').length > 0;
                    pc.usingBundle = usingBundle;
                    var iceOptions = SDPUtils.matchPrefix(sessionpart,
                        'a=ice-options:')[0];
                    if (iceOptions) {
                        pc.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
                            .indexOf('trickle') >= 0;
                    } else {
                        pc.canTrickleIceCandidates = false;
                    }

                    sections.forEach(function(mediaSection, sdpMLineIndex) {
                        var lines = SDPUtils.splitLines(mediaSection);
                        var kind = SDPUtils.getKind(mediaSection);
                        // treat bundle-only as not-rejected.
                        var rejected = SDPUtils.isRejected(mediaSection) &&
                            SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;
                        var protocol = lines[0].substr(2).split(' ')[2];

                        var direction = SDPUtils.getDirection(mediaSection, sessionpart);
                        var remoteMsid = SDPUtils.parseMsid(mediaSection);

                        var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier();

                        // Reject datachannels which are not implemented yet.
                        if ((kind === 'application' && protocol === 'DTLS/SCTP') || rejected) {
                            // TODO: this is dangerous in the case where a non-rejected m-line
                            //     becomes rejected.
                            pc.transceivers[sdpMLineIndex] = {
                                mid: mid,
                                kind: kind,
                                rejected: true
                            };
                            return;
                        }

                        if (!rejected && pc.transceivers[sdpMLineIndex] &&
                            pc.transceivers[sdpMLineIndex].rejected) {
                            // recycle a rejected transceiver.
                            pc.transceivers[sdpMLineIndex] = pc._createTransceiver(kind, true);
                        }

                        var transceiver;
                        var iceGatherer;
                        var iceTransport;
                        var dtlsTransport;
                        var rtpReceiver;
                        var sendEncodingParameters;
                        var recvEncodingParameters;
                        var localCapabilities;

                        var track;
                        // FIXME: ensure the mediaSection has rtcp-mux set.
                        var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
                        var remoteIceParameters;
                        var remoteDtlsParameters;
                        if (!rejected) {
                            remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
                                sessionpart);
                            remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
                                sessionpart);
                            remoteDtlsParameters.role = 'client';
                        }
                        recvEncodingParameters =
                            SDPUtils.parseRtpEncodingParameters(mediaSection);

                        var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection);

                        var isComplete = SDPUtils.matchPrefix(mediaSection,
                            'a=end-of-candidates', sessionpart).length > 0;
                        var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
                            .map(function(cand) {
                                return SDPUtils.parseCandidate(cand);
                            })
                            .filter(function(cand) {
                                return cand.component === 1;
                            });

                        // Check if we can use BUNDLE and dispose transports.
                        if ((description.type === 'offer' || description.type === 'answer') &&
                            !rejected && usingBundle && sdpMLineIndex > 0 &&
                            pc.transceivers[sdpMLineIndex]) {
                            pc._disposeIceAndDtlsTransports(sdpMLineIndex);
                            pc.transceivers[sdpMLineIndex].iceGatherer =
                                pc.transceivers[0].iceGatherer;
                            pc.transceivers[sdpMLineIndex].iceTransport =
                                pc.transceivers[0].iceTransport;
                            pc.transceivers[sdpMLineIndex].dtlsTransport =
                                pc.transceivers[0].dtlsTransport;
                            if (pc.transceivers[sdpMLineIndex].rtpSender) {
                                pc.transceivers[sdpMLineIndex].rtpSender.setTransport(
                                    pc.transceivers[0].dtlsTransport);
                            }
                            if (pc.transceivers[sdpMLineIndex].rtpReceiver) {
                                pc.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
                                    pc.transceivers[0].dtlsTransport);
                            }
                        }
                        if (description.type === 'offer' && !rejected) {
                            transceiver = pc.transceivers[sdpMLineIndex] ||
                                pc._createTransceiver(kind);
                            transceiver.mid = mid;

                            if (!transceiver.iceGatherer) {
                                transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                                    usingBundle);
                            }

                            if (cands.length && transceiver.iceTransport.state === 'new') {
                                if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
                                    transceiver.iceTransport.setRemoteCandidates(cands);
                                } else {
                                    cands.forEach(function(candidate) {
                                        maybeAddCandidate(transceiver.iceTransport, candidate);
                                    });
                                }
                            }

                            localCapabilities = window.RTCRtpReceiver.getCapabilities(kind);

                            // filter RTX until additional stuff needed for RTX is implemented
                            // in adapter.js
                            if (edgeVersion < 15019) {
                                localCapabilities.codecs = localCapabilities.codecs.filter(
                                    function(codec) {
                                        return codec.name !== 'rtx';
                                    });
                            }

                            sendEncodingParameters = transceiver.sendEncodingParameters || [{
                                ssrc: (2 * sdpMLineIndex + 2) * 1001
                            }];

                            // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
                            var isNewTrack = false;
                            if (direction === 'sendrecv' || direction === 'sendonly') {
                                isNewTrack = !transceiver.rtpReceiver;
                                rtpReceiver = transceiver.rtpReceiver ||
                                    new window.RTCRtpReceiver(transceiver.dtlsTransport, kind);

                                if (isNewTrack) {
                                    var stream;
                                    track = rtpReceiver.track;
                                    // FIXME: does not work with Plan B.
                                    if (remoteMsid && remoteMsid.stream === '-') {
                                        // no-op. a stream id of '-' means: no associated stream.
                                    } else if (remoteMsid) {
                                        if (!streams[remoteMsid.stream]) {
                                            streams[remoteMsid.stream] = new window.MediaStream();
                                            Object.defineProperty(streams[remoteMsid.stream], 'id', {
                                                get: function() {
                                                    return remoteMsid.stream;
                                                }
                                            });
                                        }
                                        Object.defineProperty(track, 'id', {
                                            get: function() {
                                                return remoteMsid.track;
                                            }
                                        });
                                        stream = streams[remoteMsid.stream];
                                    } else {
                                        if (!streams.default) {
                                            streams.default = new window.MediaStream();
                                        }
                                        stream = streams.default;
                                    }
                                    if (stream) {
                                        addTrackToStreamAndFireEvent(track, stream);
                                        transceiver.associatedRemoteMediaStreams.push(stream);
                                    }
                                    receiverList.push([track, rtpReceiver, stream]);
                                }
                            } else if (transceiver.rtpReceiver && transceiver.rtpReceiver.track) {
                                transceiver.associatedRemoteMediaStreams.forEach(function(s) {
                                    var nativeTrack = s.getTracks().find(function(t) {
                                        return t.id === transceiver.rtpReceiver.track.id;
                                    });
                                    if (nativeTrack) {
                                        removeTrackFromStreamAndFireEvent(nativeTrack, s);
                                    }
                                });
                                transceiver.associatedRemoteMediaStreams = [];
                            }

                            transceiver.localCapabilities = localCapabilities;
                            transceiver.remoteCapabilities = remoteCapabilities;
                            transceiver.rtpReceiver = rtpReceiver;
                            transceiver.rtcpParameters = rtcpParameters;
                            transceiver.sendEncodingParameters = sendEncodingParameters;
                            transceiver.recvEncodingParameters = recvEncodingParameters;

                            // Start the RTCRtpReceiver now. The RTPSender is started in
                            // setLocalDescription.
                            pc._transceive(pc.transceivers[sdpMLineIndex],
                                false,
                                isNewTrack);
                        } else if (description.type === 'answer' && !rejected) {
                            transceiver = pc.transceivers[sdpMLineIndex];
                            iceGatherer = transceiver.iceGatherer;
                            iceTransport = transceiver.iceTransport;
                            dtlsTransport = transceiver.dtlsTransport;
                            rtpReceiver = transceiver.rtpReceiver;
                            sendEncodingParameters = transceiver.sendEncodingParameters;
                            localCapabilities = transceiver.localCapabilities;

                            pc.transceivers[sdpMLineIndex].recvEncodingParameters =
                                recvEncodingParameters;
                            pc.transceivers[sdpMLineIndex].remoteCapabilities =
                                remoteCapabilities;
                            pc.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters;

                            if (cands.length && iceTransport.state === 'new') {
                                if ((isIceLite || isComplete) &&
                                    (!usingBundle || sdpMLineIndex === 0)) {
                                    iceTransport.setRemoteCandidates(cands);
                                } else {
                                    cands.forEach(function(candidate) {
                                        maybeAddCandidate(transceiver.iceTransport, candidate);
                                    });
                                }
                            }

                            if (!usingBundle || sdpMLineIndex === 0) {
                                if (iceTransport.state === 'new') {
                                    iceTransport.start(iceGatherer, remoteIceParameters,
                                        'controlling');
                                }
                                if (dtlsTransport.state === 'new') {
                                    dtlsTransport.start(remoteDtlsParameters);
                                }
                            }

                            pc._transceive(transceiver,
                                direction === 'sendrecv' || direction === 'recvonly',
                                direction === 'sendrecv' || direction === 'sendonly');

                            // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
                            if (rtpReceiver &&
                                (direction === 'sendrecv' || direction === 'sendonly')) {
                                track = rtpReceiver.track;
                                if (remoteMsid) {
                                    if (!streams[remoteMsid.stream]) {
                                        streams[remoteMsid.stream] = new window.MediaStream();
                                    }
                                    addTrackToStreamAndFireEvent(track, streams[remoteMsid.stream]);
                                    receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]]);
                                } else {
                                    if (!streams.default) {
                                        streams.default = new window.MediaStream();
                                    }
                                    addTrackToStreamAndFireEvent(track, streams.default);
                                    receiverList.push([track, rtpReceiver, streams.default]);
                                }
                            } else {
                                // FIXME: actually the receiver should be created later.
                                delete transceiver.rtpReceiver;
                            }
                        }
                    });

                    if (pc._dtlsRole === undefined) {
                        pc._dtlsRole = description.type === 'offer' ? 'active' : 'passive';
                    }

                    pc.remoteDescription = {
                        type: description.type,
                        sdp: description.sdp
                    };
                    if (description.type === 'offer') {
                        pc._updateSignalingState('have-remote-offer');
                    } else {
                        pc._updateSignalingState('stable');
                    }
                    Object.keys(streams).forEach(function(sid) {
                        var stream = streams[sid];
                        if (stream.getTracks().length) {
                            if (pc.remoteStreams.indexOf(stream) === -1) {
                                pc.remoteStreams.push(stream);
                                var event = new Event('addstream');
                                event.stream = stream;
                                window.setTimeout(function() {
                                    pc._dispatchEvent('addstream', event);
                                });
                            }

                            receiverList.forEach(function(item) {
                                var track = item[0];
                                var receiver = item[1];
                                if (stream.id !== item[2].id) {
                                    return;
                                }
                                fireAddTrack(pc, track, receiver, [stream]);
                            });
                        }
                    });
                    receiverList.forEach(function(item) {
                        if (item[2]) {
                            return;
                        }
                        fireAddTrack(pc, item[0], item[1], []);
                    });

                    // check whether addIceCandidate({}) was called within four seconds after
                    // setRemoteDescription.
                    window.setTimeout(function() {
                        if (!(pc && pc.transceivers)) {
                            return;
                        }
                        pc.transceivers.forEach(function(transceiver) {
                            if (transceiver.iceTransport &&
                                transceiver.iceTransport.state === 'new' &&
                                transceiver.iceTransport.getRemoteCandidates().length > 0) {
                                console.warn('Timeout for addRemoteCandidate. Consider sending ' +
                                    'an end-of-candidates notification');
                                transceiver.iceTransport.addRemoteCandidate({});
                            }
                        });
                    }, 4000);

                    return Promise.resolve();
                };

                RTCPeerConnection.prototype.close = function() {
                    this.transceivers.forEach(function(transceiver) {
                        /* not yet
                        if (transceiver.iceGatherer) {
                          transceiver.iceGatherer.close();
                        }
                        */
                        if (transceiver.iceTransport) {
                            transceiver.iceTransport.stop();
                        }
                        if (transceiver.dtlsTransport) {
                            transceiver.dtlsTransport.stop();
                        }
                        if (transceiver.rtpSender) {
                            transceiver.rtpSender.stop();
                        }
                        if (transceiver.rtpReceiver) {
                            transceiver.rtpReceiver.stop();
                        }
                    });
                    // FIXME: clean up tracks, local streams, remote streams, etc
                    this._isClosed = true;
                    this._updateSignalingState('closed');
                };

                // Update the signaling state.
                RTCPeerConnection.prototype._updateSignalingState = function(newState) {
                    this.signalingState = newState;
                    var event = new Event('signalingstatechange');
                    this._dispatchEvent('signalingstatechange', event);
                };

                // Determine whether to fire the negotiationneeded event.
                RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
                    var pc = this;
                    if (this.signalingState !== 'stable' || this.needNegotiation === true) {
                        return;
                    }
                    this.needNegotiation = true;
                    window.setTimeout(function() {
                        if (pc.needNegotiation) {
                            pc.needNegotiation = false;
                            var event = new Event('negotiationneeded');
                            pc._dispatchEvent('negotiationneeded', event);
                        }
                    }, 0);
                };

                // Update the ice connection state.
                RTCPeerConnection.prototype._updateIceConnectionState = function() {
                    var newState;
                    var states = {
                        'new': 0,
                        closed: 0,
                        checking: 0,
                        connected: 0,
                        completed: 0,
                        disconnected: 0,
                        failed: 0
                    };
                    this.transceivers.forEach(function(transceiver) {
                        states[transceiver.iceTransport.state]++;
                    });

                    newState = 'new';
                    if (states.failed > 0) {
                        newState = 'failed';
                    } else if (states.checking > 0) {
                        newState = 'checking';
                    } else if (states.disconnected > 0) {
                        newState = 'disconnected';
                    } else if (states.new > 0) {
                        newState = 'new';
                    } else if (states.connected > 0) {
                        newState = 'connected';
                    } else if (states.completed > 0) {
                        newState = 'completed';
                    }

                    if (newState !== this.iceConnectionState) {
                        this.iceConnectionState = newState;
                        var event = new Event('iceconnectionstatechange');
                        this._dispatchEvent('iceconnectionstatechange', event);
                    }
                };

                // Update the connection state.
                RTCPeerConnection.prototype._updateConnectionState = function() {
                    var newState;
                    var states = {
                        'new': 0,
                        closed: 0,
                        connecting: 0,
                        connected: 0,
                        completed: 0,
                        disconnected: 0,
                        failed: 0
                    };
                    this.transceivers.forEach(function(transceiver) {
                        states[transceiver.iceTransport.state]++;
                        states[transceiver.dtlsTransport.state]++;
                    });
                    // ICETransport.completed and connected are the same for this purpose.
                    states.connected += states.completed;

                    newState = 'new';
                    if (states.failed > 0) {
                        newState = 'failed';
                    } else if (states.connecting > 0) {
                        newState = 'connecting';
                    } else if (states.disconnected > 0) {
                        newState = 'disconnected';
                    } else if (states.new > 0) {
                        newState = 'new';
                    } else if (states.connected > 0) {
                        newState = 'connected';
                    }

                    if (newState !== this.connectionState) {
                        this.connectionState = newState;
                        var event = new Event('connectionstatechange');
                        this._dispatchEvent('connectionstatechange', event);
                    }
                };

                RTCPeerConnection.prototype.createOffer = function() {
                    var pc = this;

                    if (pc._isClosed) {
                        return Promise.reject(makeError('InvalidStateError',
                            'Can not call createOffer after close'));
                    }

                    var numAudioTracks = pc.transceivers.filter(function(t) {
                        return t.kind === 'audio';
                    }).length;
                    var numVideoTracks = pc.transceivers.filter(function(t) {
                        return t.kind === 'video';
                    }).length;

                    // Determine number of audio and video tracks we need to send/recv.
                    var offerOptions = arguments[0];
                    if (offerOptions) {
                        // Reject Chrome legacy constraints.
                        if (offerOptions.mandatory || offerOptions.optional) {
                            throw new TypeError(
                                'Legacy mandatory/optional constraints not supported.');
                        }
                        if (offerOptions.offerToReceiveAudio !== undefined) {
                            if (offerOptions.offerToReceiveAudio === true) {
                                numAudioTracks = 1;
                            } else if (offerOptions.offerToReceiveAudio === false) {
                                numAudioTracks = 0;
                            } else {
                                numAudioTracks = offerOptions.offerToReceiveAudio;
                            }
                        }
                        if (offerOptions.offerToReceiveVideo !== undefined) {
                            if (offerOptions.offerToReceiveVideo === true) {
                                numVideoTracks = 1;
                            } else if (offerOptions.offerToReceiveVideo === false) {
                                numVideoTracks = 0;
                            } else {
                                numVideoTracks = offerOptions.offerToReceiveVideo;
                            }
                        }
                    }

                    pc.transceivers.forEach(function(transceiver) {
                        if (transceiver.kind === 'audio') {
                            numAudioTracks--;
                            if (numAudioTracks < 0) {
                                transceiver.wantReceive = false;
                            }
                        } else if (transceiver.kind === 'video') {
                            numVideoTracks--;
                            if (numVideoTracks < 0) {
                                transceiver.wantReceive = false;
                            }
                        }
                    });

                    // Create M-lines for recvonly streams.
                    while (numAudioTracks > 0 || numVideoTracks > 0) {
                        if (numAudioTracks > 0) {
                            pc._createTransceiver('audio');
                            numAudioTracks--;
                        }
                        if (numVideoTracks > 0) {
                            pc._createTransceiver('video');
                            numVideoTracks--;
                        }
                    }

                    var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
                        pc._sdpSessionVersion++);
                    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                        // For each track, create an ice gatherer, ice transport,
                        // dtls transport, potentially rtpsender and rtpreceiver.
                        var track = transceiver.track;
                        var kind = transceiver.kind;
                        var mid = transceiver.mid || SDPUtils.generateIdentifier();
                        transceiver.mid = mid;

                        if (!transceiver.iceGatherer) {
                            transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                                pc.usingBundle);
                        }

                        var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
                        // filter RTX until additional stuff needed for RTX is implemented
                        // in adapter.js
                        if (edgeVersion < 15019) {
                            localCapabilities.codecs = localCapabilities.codecs.filter(
                                function(codec) {
                                    return codec.name !== 'rtx';
                                });
                        }
                        localCapabilities.codecs.forEach(function(codec) {
                            // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
                            // by adding level-asymmetry-allowed=1
                            if (codec.name === 'H264' &&
                                codec.parameters['level-asymmetry-allowed'] === undefined) {
                                codec.parameters['level-asymmetry-allowed'] = '1';
                            }

                            // for subsequent offers, we might have to re-use the payload
                            // type of the last offer.
                            if (transceiver.remoteCapabilities &&
                                transceiver.remoteCapabilities.codecs) {
                                transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
                                    if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                                        codec.clockRate === remoteCodec.clockRate) {
                                        codec.preferredPayloadType = remoteCodec.payloadType;
                                    }
                                });
                            }
                        });
                        localCapabilities.headerExtensions.forEach(function(hdrExt) {
                            var remoteExtensions = transceiver.remoteCapabilities &&
                                transceiver.remoteCapabilities.headerExtensions || [];
                            remoteExtensions.forEach(function(rHdrExt) {
                                if (hdrExt.uri === rHdrExt.uri) {
                                    hdrExt.id = rHdrExt.id;
                                }
                            });
                        });

                        // generate an ssrc now, to be used later in rtpSender.send
                        var sendEncodingParameters = transceiver.sendEncodingParameters || [{
                            ssrc: (2 * sdpMLineIndex + 1) * 1001
                        }];
                        if (track) {
                            // add RTX
                            if (edgeVersion >= 15019 && kind === 'video' &&
                                !sendEncodingParameters[0].rtx) {
                                sendEncodingParameters[0].rtx = {
                                    ssrc: sendEncodingParameters[0].ssrc + 1
                                };
                            }
                        }

                        if (transceiver.wantReceive) {
                            transceiver.rtpReceiver = new window.RTCRtpReceiver(
                                transceiver.dtlsTransport, kind);
                        }

                        transceiver.localCapabilities = localCapabilities;
                        transceiver.sendEncodingParameters = sendEncodingParameters;
                    });

                    // always offer BUNDLE and dispose on return if not supported.
                    if (pc._config.bundlePolicy !== 'max-compat') {
                        sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
                            return t.mid;
                        }).join(' ') + '\r\n';
                    }
                    sdp += 'a=ice-options:trickle\r\n';

                    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                        sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
                            'offer', transceiver.stream, pc._dtlsRole);
                        sdp += 'a=rtcp-rsize\r\n';

                        if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
                            (sdpMLineIndex === 0 || !pc.usingBundle)) {
                            transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
                                cand.component = 1;
                                sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
                            });

                            if (transceiver.iceGatherer.state === 'completed') {
                                sdp += 'a=end-of-candidates\r\n';
                            }
                        }
                    });

                    var desc = new window.RTCSessionDescription({
                        type: 'offer',
                        sdp: sdp
                    });
                    return Promise.resolve(desc);
                };

                RTCPeerConnection.prototype.createAnswer = function() {
                    var pc = this;

                    if (pc._isClosed) {
                        return Promise.reject(makeError('InvalidStateError',
                            'Can not call createAnswer after close'));
                    }

                    if (!(pc.signalingState === 'have-remote-offer' ||
                            pc.signalingState === 'have-local-pranswer')) {
                        return Promise.reject(makeError('InvalidStateError',
                            'Can not call createAnswer in signalingState ' + pc.signalingState));
                    }

                    var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
                        pc._sdpSessionVersion++);
                    if (pc.usingBundle) {
                        sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
                            return t.mid;
                        }).join(' ') + '\r\n';
                    }
                    var mediaSectionsInOffer = SDPUtils.getMediaSections(
                        pc.remoteDescription.sdp).length;
                    pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                        if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
                            return;
                        }
                        if (transceiver.rejected) {
                            if (transceiver.kind === 'application') {
                                sdp += 'm=application 0 DTLS/SCTP 5000\r\n';
                            } else if (transceiver.kind === 'audio') {
                                sdp += 'm=audio 0 UDP/TLS/RTP/SAVPF 0\r\n' +
                                    'a=rtpmap:0 PCMU/8000\r\n';
                            } else if (transceiver.kind === 'video') {
                                sdp += 'm=video 0 UDP/TLS/RTP/SAVPF 120\r\n' +
                                    'a=rtpmap:120 VP8/90000\r\n';
                            }
                            sdp += 'c=IN IP4 0.0.0.0\r\n' +
                                'a=inactive\r\n' +
                                'a=mid:' + transceiver.mid + '\r\n';
                            return;
                        }

                        // FIXME: look at direction.
                        if (transceiver.stream) {
                            var localTrack;
                            if (transceiver.kind === 'audio') {
                                localTrack = transceiver.stream.getAudioTracks()[0];
                            } else if (transceiver.kind === 'video') {
                                localTrack = transceiver.stream.getVideoTracks()[0];
                            }
                            if (localTrack) {
                                // add RTX
                                if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
                                    !transceiver.sendEncodingParameters[0].rtx) {
                                    transceiver.sendEncodingParameters[0].rtx = {
                                        ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
                                    };
                                }
                            }
                        }

                        // Calculate intersection of capabilities.
                        var commonCapabilities = getCommonCapabilities(
                            transceiver.localCapabilities,
                            transceiver.remoteCapabilities);

                        var hasRtx = commonCapabilities.codecs.filter(function(c) {
                            return c.name.toLowerCase() === 'rtx';
                        }).length;
                        if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
                            delete transceiver.sendEncodingParameters[0].rtx;
                        }

                        sdp += writeMediaSection(transceiver, commonCapabilities,
                            'answer', transceiver.stream, pc._dtlsRole);
                        if (transceiver.rtcpParameters &&
                            transceiver.rtcpParameters.reducedSize) {
                            sdp += 'a=rtcp-rsize\r\n';
                        }
                    });

                    var desc = new window.RTCSessionDescription({
                        type: 'answer',
                        sdp: sdp
                    });
                    return Promise.resolve(desc);
                };

                RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
                    var pc = this;
                    var sections;
                    if (candidate && !(candidate.sdpMLineIndex !== undefined ||
                            candidate.sdpMid)) {
                        return Promise.reject(new TypeError('sdpMLineIndex or sdpMid required'));
                    }

                    // TODO: needs to go into ops queue.
                    return new Promise(function(resolve, reject) {
                        if (!pc.remoteDescription) {
                            return reject(makeError('InvalidStateError',
                                'Can not add ICE candidate without a remote description'));
                        } else if (!candidate || candidate.candidate === '') {
                            for (var j = 0; j < pc.transceivers.length; j++) {
                                if (pc.transceivers[j].rejected) {
                                    continue;
                                }
                                pc.transceivers[j].iceTransport.addRemoteCandidate({});
                                sections = SDPUtils.getMediaSections(pc.remoteDescription.sdp);
                                sections[j] += 'a=end-of-candidates\r\n';
                                pc.remoteDescription.sdp =
                                    SDPUtils.getDescription(pc.remoteDescription.sdp) +
                                    sections.join('');
                                if (pc.usingBundle) {
                                    break;
                                }
                            }
                        } else {
                            var sdpMLineIndex = candidate.sdpMLineIndex;
                            if (candidate.sdpMid) {
                                for (var i = 0; i < pc.transceivers.length; i++) {
                                    if (pc.transceivers[i].mid === candidate.sdpMid) {
                                        sdpMLineIndex = i;
                                        break;
                                    }
                                }
                            }
                            var transceiver = pc.transceivers[sdpMLineIndex];
                            if (transceiver) {
                                if (transceiver.rejected) {
                                    return resolve();
                                }
                                var cand = Object.keys(candidate.candidate).length > 0 ?
                                    SDPUtils.parseCandidate(candidate.candidate) : {};
                                // Ignore Chrome's invalid candidates since Edge does not like them.
                                if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
                                    return resolve();
                                }
                                // Ignore RTCP candidates, we assume RTCP-MUX.
                                if (cand.component && cand.component !== 1) {
                                    return resolve();
                                }
                                // when using bundle, avoid adding candidates to the wrong
                                // ice transport. And avoid adding candidates added in the SDP.
                                if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
                                        transceiver.iceTransport !== pc.transceivers[0].iceTransport)) {
                                    if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
                                        return reject(makeError('OperationError',
                                            'Can not add ICE candidate'));
                                    }
                                }

                                // update the remoteDescription.
                                var candidateString = candidate.candidate.trim();
                                if (candidateString.indexOf('a=') === 0) {
                                    candidateString = candidateString.substr(2);
                                }
                                sections = SDPUtils.getMediaSections(pc.remoteDescription.sdp);
                                sections[sdpMLineIndex] += 'a=' +
                                    (cand.type ? candidateString : 'end-of-candidates') +
                                    '\r\n';
                                pc.remoteDescription.sdp =
                                    SDPUtils.getDescription(pc.remoteDescription.sdp) +
                                    sections.join('');
                            } else {
                                return reject(makeError('OperationError',
                                    'Can not add ICE candidate'));
                            }
                        }
                        resolve();
                    });
                };

                RTCPeerConnection.prototype.getStats = function() {
                    var promises = [];
                    this.transceivers.forEach(function(transceiver) {
                        ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
                            'dtlsTransport'
                        ].forEach(function(method) {
                            if (transceiver[method]) {
                                promises.push(transceiver[method].getStats());
                            }
                        });
                    });
                    var fixStatsType = function(stat) {
                        return {
                            inboundrtp: 'inbound-rtp',
                            outboundrtp: 'outbound-rtp',
                            candidatepair: 'candidate-pair',
                            localcandidate: 'local-candidate',
                            remotecandidate: 'remote-candidate'
                        }[stat.type] || stat.type;
                    };
                    return new Promise(function(resolve) {
                        // shim getStats with maplike support
                        var results = new Map();
                        Promise.all(promises).then(function(res) {
                            res.forEach(function(result) {
                                Object.keys(result).forEach(function(id) {
                                    result[id].type = fixStatsType(result[id]);
                                    results.set(id, result[id]);
                                });
                            });
                            resolve(results);
                        });
                    });
                };

                // legacy callback shims. Should be moved to adapter.js some days.
                var methods = ['createOffer', 'createAnswer'];
                methods.forEach(function(method) {
                    var nativeMethod = RTCPeerConnection.prototype[method];
                    RTCPeerConnection.prototype[method] = function() {
                        var args = arguments;
                        if (typeof args[0] === 'function' ||
                            typeof args[1] === 'function') { // legacy
                            return nativeMethod.apply(this, [arguments[2]])
                                .then(function(description) {
                                    if (typeof args[0] === 'function') {
                                        args[0].apply(null, [description]);
                                    }
                                }, function(error) {
                                    if (typeof args[1] === 'function') {
                                        args[1].apply(null, [error]);
                                    }
                                });
                        }
                        return nativeMethod.apply(this, arguments);
                    };
                });

                methods = ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'];
                methods.forEach(function(method) {
                    var nativeMethod = RTCPeerConnection.prototype[method];
                    RTCPeerConnection.prototype[method] = function() {
                        var args = arguments;
                        if (typeof args[1] === 'function' ||
                            typeof args[2] === 'function') { // legacy
                            return nativeMethod.apply(this, arguments)
                                .then(function() {
                                    if (typeof args[1] === 'function') {
                                        args[1].apply(null);
                                    }
                                }, function(error) {
                                    if (typeof args[2] === 'function') {
                                        args[2].apply(null, [error]);
                                    }
                                });
                        }
                        return nativeMethod.apply(this, arguments);
                    };
                });

                // getStats is special. It doesn't have a spec legacy method yet we support
                // getStats(something, cb) without error callbacks.
                ['getStats'].forEach(function(method) {
                    var nativeMethod = RTCPeerConnection.prototype[method];
                    RTCPeerConnection.prototype[method] = function() {
                        var args = arguments;
                        if (typeof args[1] === 'function') {
                            return nativeMethod.apply(this, arguments)
                                .then(function() {
                                    if (typeof args[1] === 'function') {
                                        args[1].apply(null);
                                    }
                                });
                        }
                        return nativeMethod.apply(this, arguments);
                    };
                });

                return RTCPeerConnection;
            };

        }, {
            "sdp": 2
        }],
        2: [function(require, module, exports) {
            /* eslint-env node */
            'use strict';

            // SDP helpers.
            var SDPUtils = {};

            // Generate an alphanumeric identifier for cname or mids.
            // TODO: use UUIDs instead? https://gist.github.com/jed/982883
            SDPUtils.generateIdentifier = function() {
                return Math.random().toString(36).substr(2, 10);
            };

            // The RTCP CNAME used by all peerconnections from the same JS.
            SDPUtils.localCName = SDPUtils.generateIdentifier();

            // Splits SDP into lines, dealing with both CRLF and LF.
            SDPUtils.splitLines = function(blob) {
                return blob.trim().split('\n').map(function(line) {
                    return line.trim();
                });
            };
            // Splits SDP into sessionpart and mediasections. Ensures CRLF.
            SDPUtils.splitSections = function(blob) {
                var parts = blob.split('\nm=');
                return parts.map(function(part, index) {
                    return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
                });
            };

            // returns the session description.
            SDPUtils.getDescription = function(blob) {
                var sections = SDPUtils.splitSections(blob);
                return sections && sections[0];
            };

            // returns the individual media sections.
            SDPUtils.getMediaSections = function(blob) {
                var sections = SDPUtils.splitSections(blob);
                sections.shift();
                return sections;
            };

            // Returns lines that start with a certain prefix.
            SDPUtils.matchPrefix = function(blob, prefix) {
                return SDPUtils.splitLines(blob).filter(function(line) {
                    return line.indexOf(prefix) === 0;
                });
            };

            // Parses an ICE candidate line. Sample input:
            // candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
            // rport 55996"
            SDPUtils.parseCandidate = function(line) {
                var parts;
                // Parse both variants.
                if (line.indexOf('a=candidate:') === 0) {
                    parts = line.substring(12).split(' ');
                } else {
                    parts = line.substring(10).split(' ');
                }

                var candidate = {
                    foundation: parts[0],
                    component: parseInt(parts[1], 10),
                    protocol: parts[2].toLowerCase(),
                    priority: parseInt(parts[3], 10),
                    ip: parts[4],
                    port: parseInt(parts[5], 10),
                    // skip parts[6] == 'typ'
                    type: parts[7]
                };

                for (var i = 8; i < parts.length; i += 2) {
                    switch (parts[i]) {
                        case 'raddr':
                            candidate.relatedAddress = parts[i + 1];
                            break;
                        case 'rport':
                            candidate.relatedPort = parseInt(parts[i + 1], 10);
                            break;
                        case 'tcptype':
                            candidate.tcpType = parts[i + 1];
                            break;
                        case 'ufrag':
                            candidate.ufrag = parts[i + 1]; // for backward compability.
                            candidate.usernameFragment = parts[i + 1];
                            break;
                        default: // extension handling, in particular ufrag
                            candidate[parts[i]] = parts[i + 1];
                            break;
                    }
                }
                return candidate;
            };

            // Translates a candidate object into SDP candidate attribute.
            SDPUtils.writeCandidate = function(candidate) {
                var sdp = [];
                sdp.push(candidate.foundation);
                sdp.push(candidate.component);
                sdp.push(candidate.protocol.toUpperCase());
                sdp.push(candidate.priority);
                sdp.push(candidate.ip);
                sdp.push(candidate.port);

                var type = candidate.type;
                sdp.push('typ');
                sdp.push(type);
                if (type !== 'host' && candidate.relatedAddress &&
                    candidate.relatedPort) {
                    sdp.push('raddr');
                    sdp.push(candidate.relatedAddress); // was: relAddr
                    sdp.push('rport');
                    sdp.push(candidate.relatedPort); // was: relPort
                }
                if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
                    sdp.push('tcptype');
                    sdp.push(candidate.tcpType);
                }
                if (candidate.usernameFragment || candidate.ufrag) {
                    sdp.push('ufrag');
                    sdp.push(candidate.usernameFragment || candidate.ufrag);
                }
                return 'candidate:' + sdp.join(' ');
            };

            // Parses an ice-options line, returns an array of option tags.
            // a=ice-options:foo bar
            SDPUtils.parseIceOptions = function(line) {
                return line.substr(14).split(' ');
            }

            // Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
            // a=rtpmap:111 opus/48000/2
            SDPUtils.parseRtpMap = function(line) {
                var parts = line.substr(9).split(' ');
                var parsed = {
                    payloadType: parseInt(parts.shift(), 10) // was: id
                };

                parts = parts[0].split('/');

                parsed.name = parts[0];
                parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
                // was: channels
                parsed.numChannels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
                return parsed;
            };

            // Generate an a=rtpmap line from RTCRtpCodecCapability or
            // RTCRtpCodecParameters.
            SDPUtils.writeRtpMap = function(codec) {
                var pt = codec.payloadType;
                if (codec.preferredPayloadType !== undefined) {
                    pt = codec.preferredPayloadType;
                }
                return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
                    (codec.numChannels !== 1 ? '/' + codec.numChannels : '') + '\r\n';
            };

            // Parses an a=extmap line (headerextension from RFC 5285). Sample input:
            // a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
            // a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
            SDPUtils.parseExtmap = function(line) {
                var parts = line.substr(9).split(' ');
                return {
                    id: parseInt(parts[0], 10),
                    direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
                    uri: parts[1]
                };
            };

            // Generates a=extmap line from RTCRtpHeaderExtensionParameters or
            // RTCRtpHeaderExtension.
            SDPUtils.writeExtmap = function(headerExtension) {
                return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
                    (headerExtension.direction && headerExtension.direction !== 'sendrecv' ?
                        '/' + headerExtension.direction :
                        '') +
                    ' ' + headerExtension.uri + '\r\n';
            };

            // Parses an ftmp line, returns dictionary. Sample input:
            // a=fmtp:96 vbr=on;cng=on
            // Also deals with vbr=on; cng=on
            SDPUtils.parseFmtp = function(line) {
                var parsed = {};
                var kv;
                var parts = line.substr(line.indexOf(' ') + 1).split(';');
                for (var j = 0; j < parts.length; j++) {
                    kv = parts[j].trim().split('=');
                    parsed[kv[0].trim()] = kv[1];
                }
                return parsed;
            };

            // Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
            SDPUtils.writeFmtp = function(codec) {
                var line = '';
                var pt = codec.payloadType;
                if (codec.preferredPayloadType !== undefined) {
                    pt = codec.preferredPayloadType;
                }
                if (codec.parameters && Object.keys(codec.parameters).length) {
                    var params = [];
                    Object.keys(codec.parameters).forEach(function(param) {
                        params.push(param + '=' + codec.parameters[param]);
                    });
                    line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
                }
                return line;
            };

            // Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
            // a=rtcp-fb:98 nack rpsi
            SDPUtils.parseRtcpFb = function(line) {
                var parts = line.substr(line.indexOf(' ') + 1).split(' ');
                return {
                    type: parts.shift(),
                    parameter: parts.join(' ')
                };
            };
            // Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
            SDPUtils.writeRtcpFb = function(codec) {
                var lines = '';
                var pt = codec.payloadType;
                if (codec.preferredPayloadType !== undefined) {
                    pt = codec.preferredPayloadType;
                }
                if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
                    // FIXME: special handling for trr-int?
                    codec.rtcpFeedback.forEach(function(fb) {
                        lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
                            (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
                            '\r\n';
                    });
                }
                return lines;
            };

            // Parses an RFC 5576 ssrc media attribute. Sample input:
            // a=ssrc:3735928559 cname:something
            SDPUtils.parseSsrcMedia = function(line) {
                var sp = line.indexOf(' ');
                var parts = {
                    ssrc: parseInt(line.substr(7, sp - 7), 10)
                };
                var colon = line.indexOf(':', sp);
                if (colon > -1) {
                    parts.attribute = line.substr(sp + 1, colon - sp - 1);
                    parts.value = line.substr(colon + 1);
                } else {
                    parts.attribute = line.substr(sp + 1);
                }
                return parts;
            };

            // Extracts the MID (RFC 5888) from a media section.
            // returns the MID or undefined if no mid line was found.
            SDPUtils.getMid = function(mediaSection) {
                var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
                if (mid) {
                    return mid.substr(6);
                }
            }

            SDPUtils.parseFingerprint = function(line) {
                var parts = line.substr(14).split(' ');
                return {
                    algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
                    value: parts[1]
                };
            };

            // Extracts DTLS parameters from SDP media section or sessionpart.
            // FIXME: for consistency with other functions this should only
            //   get the fingerprint line as input. See also getIceParameters.
            SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
                var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
                    'a=fingerprint:');
                // Note: a=setup line is ignored since we use the 'auto' role.
                // Note2: 'algorithm' is not case sensitive except in Edge.
                return {
                    role: 'auto',
                    fingerprints: lines.map(SDPUtils.parseFingerprint)
                };
            };

            // Serializes DTLS parameters to SDP.
            SDPUtils.writeDtlsParameters = function(params, setupType) {
                var sdp = 'a=setup:' + setupType + '\r\n';
                params.fingerprints.forEach(function(fp) {
                    sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
                });
                return sdp;
            };
            // Parses ICE information from SDP media section or sessionpart.
            // FIXME: for consistency with other functions this should only
            //   get the ice-ufrag and ice-pwd lines as input.
            SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
                var lines = SDPUtils.splitLines(mediaSection);
                // Search in session part, too.
                lines = lines.concat(SDPUtils.splitLines(sessionpart));
                var iceParameters = {
                    usernameFragment: lines.filter(function(line) {
                        return line.indexOf('a=ice-ufrag:') === 0;
                    })[0].substr(12),
                    password: lines.filter(function(line) {
                        return line.indexOf('a=ice-pwd:') === 0;
                    })[0].substr(10)
                };
                return iceParameters;
            };

            // Serializes ICE parameters to SDP.
            SDPUtils.writeIceParameters = function(params) {
                return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
                    'a=ice-pwd:' + params.password + '\r\n';
            };

            // Parses the SDP media section and returns RTCRtpParameters.
            SDPUtils.parseRtpParameters = function(mediaSection) {
                var description = {
                    codecs: [],
                    headerExtensions: [],
                    fecMechanisms: [],
                    rtcp: []
                };
                var lines = SDPUtils.splitLines(mediaSection);
                var mline = lines[0].split(' ');
                for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
                    var pt = mline[i];
                    var rtpmapline = SDPUtils.matchPrefix(
                        mediaSection, 'a=rtpmap:' + pt + ' ')[0];
                    if (rtpmapline) {
                        var codec = SDPUtils.parseRtpMap(rtpmapline);
                        var fmtps = SDPUtils.matchPrefix(
                            mediaSection, 'a=fmtp:' + pt + ' ');
                        // Only the first a=fmtp:<pt> is considered.
                        codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
                        codec.rtcpFeedback = SDPUtils.matchPrefix(
                                mediaSection, 'a=rtcp-fb:' + pt + ' ')
                            .map(SDPUtils.parseRtcpFb);
                        description.codecs.push(codec);
                        // parse FEC mechanisms from rtpmap lines.
                        switch (codec.name.toUpperCase()) {
                            case 'RED':
                            case 'ULPFEC':
                                description.fecMechanisms.push(codec.name.toUpperCase());
                                break;
                            default: // only RED and ULPFEC are recognized as FEC mechanisms.
                                break;
                        }
                    }
                }
                SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
                    description.headerExtensions.push(SDPUtils.parseExtmap(line));
                });
                // FIXME: parse rtcp.
                return description;
            };

            // Generates parts of the SDP media section describing the capabilities /
            // parameters.
            SDPUtils.writeRtpDescription = function(kind, caps) {
                var sdp = '';

                // Build the mline.
                sdp += 'm=' + kind + ' ';
                sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
                sdp += ' UDP/TLS/RTP/SAVPF ';
                sdp += caps.codecs.map(function(codec) {
                    if (codec.preferredPayloadType !== undefined) {
                        return codec.preferredPayloadType;
                    }
                    return codec.payloadType;
                }).join(' ') + '\r\n';

                sdp += 'c=IN IP4 0.0.0.0\r\n';
                sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';

                // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
                caps.codecs.forEach(function(codec) {
                    sdp += SDPUtils.writeRtpMap(codec);
                    sdp += SDPUtils.writeFmtp(codec);
                    sdp += SDPUtils.writeRtcpFb(codec);
                });
                var maxptime = 0;
                caps.codecs.forEach(function(codec) {
                    if (codec.maxptime > maxptime) {
                        maxptime = codec.maxptime;
                    }
                });
                if (maxptime > 0) {
                    sdp += 'a=maxptime:' + maxptime + '\r\n';
                }
                sdp += 'a=rtcp-mux\r\n';

                caps.headerExtensions.forEach(function(extension) {
                    sdp += SDPUtils.writeExtmap(extension);
                });
                // FIXME: write fecMechanisms.
                return sdp;
            };

            // Parses the SDP media section and returns an array of
            // RTCRtpEncodingParameters.
            SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
                var encodingParameters = [];
                var description = SDPUtils.parseRtpParameters(mediaSection);
                var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
                var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;

                // filter a=ssrc:... cname:, ignore PlanB-msid
                var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
                    .map(function(line) {
                        return SDPUtils.parseSsrcMedia(line);
                    })
                    .filter(function(parts) {
                        return parts.attribute === 'cname';
                    });
                var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
                var secondarySsrc;

                var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
                    .map(function(line) {
                        var parts = line.split(' ');
                        parts.shift();
                        return parts.map(function(part) {
                            return parseInt(part, 10);
                        });
                    });
                if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
                    secondarySsrc = flows[0][1];
                }

                description.codecs.forEach(function(codec) {
                    if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
                        var encParam = {
                            ssrc: primarySsrc,
                            codecPayloadType: parseInt(codec.parameters.apt, 10),
                            rtx: {
                                ssrc: secondarySsrc
                            }
                        };
                        encodingParameters.push(encParam);
                        if (hasRed) {
                            encParam = JSON.parse(JSON.stringify(encParam));
                            encParam.fec = {
                                ssrc: secondarySsrc,
                                mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
                            };
                            encodingParameters.push(encParam);
                        }
                    }
                });
                if (encodingParameters.length === 0 && primarySsrc) {
                    encodingParameters.push({
                        ssrc: primarySsrc
                    });
                }

                // we support both b=AS and b=TIAS but interpret AS as TIAS.
                var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
                if (bandwidth.length) {
                    if (bandwidth[0].indexOf('b=TIAS:') === 0) {
                        bandwidth = parseInt(bandwidth[0].substr(7), 10);
                    } else if (bandwidth[0].indexOf('b=AS:') === 0) {
                        // use formula from JSEP to convert b=AS to TIAS value.
                        bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95 -
                            (50 * 40 * 8);
                    } else {
                        bandwidth = undefined;
                    }
                    encodingParameters.forEach(function(params) {
                        params.maxBitrate = bandwidth;
                    });
                }
                return encodingParameters;
            };

            // parses http://draft.ortc.org/#rtcrtcpparameters*
            SDPUtils.parseRtcpParameters = function(mediaSection) {
                var rtcpParameters = {};

                var cname;
                // Gets the first SSRC. Note that with RTX there might be multiple
                // SSRCs.
                var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
                    .map(function(line) {
                        return SDPUtils.parseSsrcMedia(line);
                    })
                    .filter(function(obj) {
                        return obj.attribute === 'cname';
                    })[0];
                if (remoteSsrc) {
                    rtcpParameters.cname = remoteSsrc.value;
                    rtcpParameters.ssrc = remoteSsrc.ssrc;
                }

                // Edge uses the compound attribute instead of reducedSize
                // compound is !reducedSize
                var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
                rtcpParameters.reducedSize = rsize.length > 0;
                rtcpParameters.compound = rsize.length === 0;

                // parses the rtcp-mux attrіbute.
                // Note that Edge does not support unmuxed RTCP.
                var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
                rtcpParameters.mux = mux.length > 0;

                return rtcpParameters;
            };

            // parses either a=msid: or a=ssrc:... msid lines and returns
            // the id of the MediaStream and MediaStreamTrack.
            SDPUtils.parseMsid = function(mediaSection) {
                var parts;
                var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
                if (spec.length === 1) {
                    parts = spec[0].substr(7).split(' ');
                    return {
                        stream: parts[0],
                        track: parts[1]
                    };
                }
                var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
                    .map(function(line) {
                        return SDPUtils.parseSsrcMedia(line);
                    })
                    .filter(function(parts) {
                        return parts.attribute === 'msid';
                    });
                if (planB.length > 0) {
                    parts = planB[0].value.split(' ');
                    return {
                        stream: parts[0],
                        track: parts[1]
                    };
                }
            };

            // Generate a session ID for SDP.
            // https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
            // recommends using a cryptographically random +ve 64-bit value
            // but right now this should be acceptable and within the right range
            SDPUtils.generateSessionId = function() {
                return Math.random().toString().substr(2, 21);
            };

            // Write boilder plate for start of SDP
            // sessId argument is optional - if not supplied it will
            // be generated randomly
            // sessVersion is optional and defaults to 2
            SDPUtils.writeSessionBoilerplate = function(sessId, sessVer) {
                var sessionId;
                var version = sessVer !== undefined ? sessVer : 2;
                if (sessId) {
                    sessionId = sessId;
                } else {
                    sessionId = SDPUtils.generateSessionId();
                }
                // FIXME: sess-id should be an NTP timestamp.
                return 'v=0\r\n' +
                    'o=thisisadapterortc ' + sessionId + ' ' + version + ' IN IP4 127.0.0.1\r\n' +
                    's=-\r\n' +
                    't=0 0\r\n';
            };

            SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
                var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

                // Map ICE parameters (ufrag, pwd) to SDP.
                sdp += SDPUtils.writeIceParameters(
                    transceiver.iceGatherer.getLocalParameters());

                // Map DTLS parameters to SDP.
                sdp += SDPUtils.writeDtlsParameters(
                    transceiver.dtlsTransport.getLocalParameters(),
                    type === 'offer' ? 'actpass' : 'active');

                sdp += 'a=mid:' + transceiver.mid + '\r\n';

                if (transceiver.direction) {
                    sdp += 'a=' + transceiver.direction + '\r\n';
                } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
                    sdp += 'a=sendrecv\r\n';
                } else if (transceiver.rtpSender) {
                    sdp += 'a=sendonly\r\n';
                } else if (transceiver.rtpReceiver) {
                    sdp += 'a=recvonly\r\n';
                } else {
                    sdp += 'a=inactive\r\n';
                }

                if (transceiver.rtpSender) {
                    // spec.
                    var msid = 'msid:' + stream.id + ' ' +
                        transceiver.rtpSender.track.id + '\r\n';
                    sdp += 'a=' + msid;

                    // for Chrome.
                    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                        ' ' + msid;
                    if (transceiver.sendEncodingParameters[0].rtx) {
                        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                            ' ' + msid;
                        sdp += 'a=ssrc-group:FID ' +
                            transceiver.sendEncodingParameters[0].ssrc + ' ' +
                            transceiver.sendEncodingParameters[0].rtx.ssrc +
                            '\r\n';
                    }
                }
                // FIXME: this should be written by writeRtpDescription.
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                    ' cname:' + SDPUtils.localCName + '\r\n';
                if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
                    sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                        ' cname:' + SDPUtils.localCName + '\r\n';
                }
                return sdp;
            };

            // Gets the direction from the mediaSection or the sessionpart.
            SDPUtils.getDirection = function(mediaSection, sessionpart) {
                // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
                var lines = SDPUtils.splitLines(mediaSection);
                for (var i = 0; i < lines.length; i++) {
                    switch (lines[i]) {
                        case 'a=sendrecv':
                        case 'a=sendonly':
                        case 'a=recvonly':
                        case 'a=inactive':
                            return lines[i].substr(2);
                        default:
                            // FIXME: What should happen here?
                    }
                }
                if (sessionpart) {
                    return SDPUtils.getDirection(sessionpart);
                }
                return 'sendrecv';
            };

            SDPUtils.getKind = function(mediaSection) {
                var lines = SDPUtils.splitLines(mediaSection);
                var mline = lines[0].split(' ');
                return mline[0].substr(2);
            };

            SDPUtils.isRejected = function(mediaSection) {
                return mediaSection.split(' ', 2)[1] === '0';
            };

            SDPUtils.parseMLine = function(mediaSection) {
                var lines = SDPUtils.splitLines(mediaSection);
                var parts = lines[0].substr(2).split(' ');
                return {
                    kind: parts[0],
                    port: parseInt(parts[1], 10),
                    protocol: parts[2],
                    fmt: parts.slice(3).join(' ')
                };
            };

            SDPUtils.parseOLine = function(mediaSection) {
                var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
                var parts = line.substr(2).split(' ');
                return {
                    username: parts[0],
                    sessionId: parts[1],
                    sessionVersion: parseInt(parts[2], 10),
                    netType: parts[3],
                    addressType: parts[4],
                    address: parts[5],
                };
            }

            // Expose public methods.
            if (typeof module === 'object') {
                module.exports = SDPUtils;
            }

        }, {}],
        3: [function(require, module, exports) {
            (function(global) {
                /*
                 *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
                 *
                 *  Use of this source code is governed by a BSD-style license
                 *  that can be found in the LICENSE file in the root of the source
                 *  tree.
                 */
                /* eslint-env node */

                'use strict';

                var adapterFactory = require('./adapter_factory.js');
                module.exports = adapterFactory({
                    window: global.window
                });

            }).call(this, typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
        }, {
            "./adapter_factory.js": 4
        }],
        4: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */

            'use strict';

            var utils = require('./utils');
            // Shimming starts here.
            module.exports = function(dependencies, opts) {
                var window = dependencies && dependencies.window;

                var options = {
                    shimChrome: true,
                    shimFirefox: true,
                    shimEdge: true,
                    shimSafari: true,
                };

                for (var key in opts) {
                    if (hasOwnProperty.call(opts, key)) {
                        options[key] = opts[key];
                    }
                }

                // Utils.
                var logging = utils.log;
                var browserDetails = utils.detectBrowser(window);

                // Uncomment the line below if you want logging to occur, including logging
                // for the switch statement below. Can also be turned on in the browser via
                // adapter.disableLog(false), but then logging from the switch statement below
                // will not appear.
                // require('./utils').disableLog(false);

                // Browser shims.
                var chromeShim = require('./chrome/chrome_shim') || null;
                var edgeShim = require('./edge/edge_shim') || null;
                var firefoxShim = require('./firefox/firefox_shim') || null;
                var safariShim = require('./safari/safari_shim') || null;
                var commonShim = require('./common_shim') || null;

                // Export to the adapter global object visible in the browser.
                var adapter = {
                    browserDetails: browserDetails,
                    commonShim: commonShim,
                    extractVersion: utils.extractVersion,
                    disableLog: utils.disableLog,
                    disableWarnings: utils.disableWarnings
                };

                // Shim browser if found.
                switch (browserDetails.browser) {
                    case 'chrome':
                        if (!chromeShim || !chromeShim.shimPeerConnection ||
                            !options.shimChrome) {
                            logging('Chrome shim is not included in this adapter release.');
                            return adapter;
                        }
                        logging('adapter.js shimming chrome.');
                        // Export to the adapter global object visible in the browser.
                        adapter.browserShim = chromeShim;
                        commonShim.shimCreateObjectURL(window);

                        chromeShim.shimGetUserMedia(window);
                        chromeShim.shimMediaStream(window);
                        chromeShim.shimSourceObject(window);
                        chromeShim.shimPeerConnection(window);
                        chromeShim.shimOnTrack(window);
                        chromeShim.shimAddTrackRemoveTrack(window);
                        chromeShim.shimGetSendersWithDtmf(window);

                        commonShim.shimRTCIceCandidate(window);
                        commonShim.shimMaxMessageSize(window);
                        commonShim.shimSendThrowTypeError(window);
                        break;
                    case 'firefox':
                        if (!firefoxShim || !firefoxShim.shimPeerConnection ||
                            !options.shimFirefox) {
                            logging('Firefox shim is not included in this adapter release.');
                            return adapter;
                        }
                        logging('adapter.js shimming firefox.');
                        // Export to the adapter global object visible in the browser.
                        adapter.browserShim = firefoxShim;
                        commonShim.shimCreateObjectURL(window);

                        firefoxShim.shimGetUserMedia(window);
                        firefoxShim.shimSourceObject(window);
                        firefoxShim.shimPeerConnection(window);
                        firefoxShim.shimOnTrack(window);
                        firefoxShim.shimRemoveStream(window);

                        commonShim.shimRTCIceCandidate(window);
                        commonShim.shimMaxMessageSize(window);
                        commonShim.shimSendThrowTypeError(window);
                        break;
                    case 'edge':
                        if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
                            logging('MS edge shim is not included in this adapter release.');
                            return adapter;
                        }
                        logging('adapter.js shimming edge.');
                        // Export to the adapter global object visible in the browser.
                        adapter.browserShim = edgeShim;
                        commonShim.shimCreateObjectURL(window);

                        edgeShim.shimGetUserMedia(window);
                        edgeShim.shimPeerConnection(window);
                        edgeShim.shimReplaceTrack(window);

                        // the edge shim implements the full RTCIceCandidate object.

                        commonShim.shimMaxMessageSize(window);
                        commonShim.shimSendThrowTypeError(window);
                        break;
                    case 'safari':
                        if (!safariShim || !options.shimSafari) {
                            logging('Safari shim is not included in this adapter release.');
                            return adapter;
                        }
                        logging('adapter.js shimming safari.');
                        // Export to the adapter global object visible in the browser.
                        adapter.browserShim = safariShim;
                        commonShim.shimCreateObjectURL(window);

                        safariShim.shimRTCIceServerUrls(window);
                        safariShim.shimCallbacksAPI(window);
                        safariShim.shimLocalStreamsAPI(window);
                        safariShim.shimRemoteStreamsAPI(window);
                        safariShim.shimTrackEventTransceiver(window);
                        safariShim.shimGetUserMedia(window);
                        safariShim.shimCreateOfferLegacy(window);

                        commonShim.shimRTCIceCandidate(window);
                        commonShim.shimMaxMessageSize(window);
                        commonShim.shimSendThrowTypeError(window);
                        break;
                    default:
                        logging('Unsupported browser!');
                        break;
                }

                return adapter;
            };

        }, {
            "./chrome/chrome_shim": 5,
            "./common_shim": 7,
            "./edge/edge_shim": 8,
            "./firefox/firefox_shim": 10,
            "./safari/safari_shim": 12,
            "./utils": 13
        }],
        5: [function(require, module, exports) {

            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';
            var utils = require('../utils.js');
            var logging = utils.log;

            module.exports = {
                shimGetUserMedia: require('./getusermedia'),
                shimMediaStream: function(window) {
                    window.MediaStream = window.MediaStream || window.webkitMediaStream;
                },

                shimOnTrack: function(window) {
                    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
                            window.RTCPeerConnection.prototype)) {
                        Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
                            get: function() {
                                return this._ontrack;
                            },
                            set: function(f) {
                                if (this._ontrack) {
                                    this.removeEventListener('track', this._ontrack);
                                }
                                this.addEventListener('track', this._ontrack = f);
                            }
                        });
                        var origSetRemoteDescription =
                            window.RTCPeerConnection.prototype.setRemoteDescription;
                        window.RTCPeerConnection.prototype.setRemoteDescription = function() {
                            var pc = this;
                            if (!pc._ontrackpoly) {
                                pc._ontrackpoly = function(e) {
                                    // onaddstream does not fire when a track is added to an existing
                                    // stream. But stream.onaddtrack is implemented so we use that.
                                    e.stream.addEventListener('addtrack', function(te) {
                                        var receiver;
                                        if (window.RTCPeerConnection.prototype.getReceivers) {
                                            receiver = pc.getReceivers().find(function(r) {
                                                return r.track && r.track.id === te.track.id;
                                            });
                                        } else {
                                            receiver = {
                                                track: te.track
                                            };
                                        }

                                        var event = new Event('track');
                                        event.track = te.track;
                                        event.receiver = receiver;
                                        event.transceiver = {
                                            receiver: receiver
                                        };
                                        event.streams = [e.stream];
                                        pc.dispatchEvent(event);
                                    });
                                    e.stream.getTracks().forEach(function(track) {
                                        var receiver;
                                        if (window.RTCPeerConnection.prototype.getReceivers) {
                                            receiver = pc.getReceivers().find(function(r) {
                                                return r.track && r.track.id === track.id;
                                            });
                                        } else {
                                            receiver = {
                                                track: track
                                            };
                                        }
                                        var event = new Event('track');
                                        event.track = track;
                                        event.receiver = receiver;
                                        event.transceiver = {
                                            receiver: receiver
                                        };
                                        event.streams = [e.stream];
                                        pc.dispatchEvent(event);
                                    });
                                };
                                pc.addEventListener('addstream', pc._ontrackpoly);
                            }
                            return origSetRemoteDescription.apply(pc, arguments);
                        };
                    } else if (!('RTCRtpTransceiver' in window)) {
                        utils.wrapPeerConnectionEvent(window, 'track', function(e) {
                            if (!e.transceiver) {
                                e.transceiver = {
                                    receiver: e.receiver
                                };
                            }
                            return e;
                        });
                    }
                },

                shimGetSendersWithDtmf: function(window) {
                    // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
                    if (typeof window === 'object' && window.RTCPeerConnection &&
                        !('getSenders' in window.RTCPeerConnection.prototype) &&
                        'createDTMFSender' in window.RTCPeerConnection.prototype) {
                        var shimSenderWithDtmf = function(pc, track) {
                            return {
                                track: track,
                                get dtmf() {
                                    if (this._dtmf === undefined) {
                                        if (track.kind === 'audio') {
                                            this._dtmf = pc.createDTMFSender(track);
                                        } else {
                                            this._dtmf = null;
                                        }
                                    }
                                    return this._dtmf;
                                },
                                _pc: pc
                            };
                        };

                        // augment addTrack when getSenders is not available.
                        if (!window.RTCPeerConnection.prototype.getSenders) {
                            window.RTCPeerConnection.prototype.getSenders = function() {
                                this._senders = this._senders || [];
                                return this._senders.slice(); // return a copy of the internal state.
                            };
                            var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
                            window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                                var pc = this;
                                var sender = origAddTrack.apply(pc, arguments);
                                if (!sender) {
                                    sender = shimSenderWithDtmf(pc, track);
                                    pc._senders.push(sender);
                                }
                                return sender;
                            };

                            var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
                            window.RTCPeerConnection.prototype.removeTrack = function(sender) {
                                var pc = this;
                                origRemoveTrack.apply(pc, arguments);
                                var idx = pc._senders.indexOf(sender);
                                if (idx !== -1) {
                                    pc._senders.splice(idx, 1);
                                }
                            };
                        }
                        var origAddStream = window.RTCPeerConnection.prototype.addStream;
                        window.RTCPeerConnection.prototype.addStream = function(stream) {
                            var pc = this;
                            pc._senders = pc._senders || [];
                            origAddStream.apply(pc, [stream]);
                            stream.getTracks().forEach(function(track) {
                                pc._senders.push(shimSenderWithDtmf(pc, track));
                            });
                        };

                        var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
                        window.RTCPeerConnection.prototype.removeStream = function(stream) {
                            var pc = this;
                            pc._senders = pc._senders || [];
                            origRemoveStream.apply(pc, [stream]);

                            stream.getTracks().forEach(function(track) {
                                var sender = pc._senders.find(function(s) {
                                    return s.track === track;
                                });
                                if (sender) {
                                    pc._senders.splice(pc._senders.indexOf(sender), 1); // remove sender
                                }
                            });
                        };
                    } else if (typeof window === 'object' && window.RTCPeerConnection &&
                        'getSenders' in window.RTCPeerConnection.prototype &&
                        'createDTMFSender' in window.RTCPeerConnection.prototype &&
                        window.RTCRtpSender &&
                        !('dtmf' in window.RTCRtpSender.prototype)) {
                        var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
                        window.RTCPeerConnection.prototype.getSenders = function() {
                            var pc = this;
                            var senders = origGetSenders.apply(pc, []);
                            senders.forEach(function(sender) {
                                sender._pc = pc;
                            });
                            return senders;
                        };

                        Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
                            get: function() {
                                if (this._dtmf === undefined) {
                                    if (this.track.kind === 'audio') {
                                        this._dtmf = this._pc.createDTMFSender(this.track);
                                    } else {
                                        this._dtmf = null;
                                    }
                                }
                                return this._dtmf;
                            }
                        });
                    }
                },

                shimSourceObject: function(window) {
                    var URL = window && window.URL;

                    if (typeof window === 'object') {
                        if (window.HTMLMediaElement &&
                            !('srcObject' in window.HTMLMediaElement.prototype)) {
                            // Shim the srcObject property, once, when HTMLMediaElement is found.
                            Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
                                get: function() {
                                    return this._srcObject;
                                },
                                set: function(stream) {
                                    var self = this;
                                    // Use _srcObject as a private property for this shim
                                    this._srcObject = stream;
                                    if (this.src) {
                                        URL.revokeObjectURL(this.src);
                                    }

                                    if (!stream) {
                                        this.src = '';
                                        return undefined;
                                    }
                                    this.src = URL.createObjectURL(stream);
                                    // We need to recreate the blob url when a track is added or
                                    // removed. Doing it manually since we want to avoid a recursion.
                                    stream.addEventListener('addtrack', function() {
                                        if (self.src) {
                                            URL.revokeObjectURL(self.src);
                                        }
                                        self.src = URL.createObjectURL(stream);
                                    });
                                    stream.addEventListener('removetrack', function() {
                                        if (self.src) {
                                            URL.revokeObjectURL(self.src);
                                        }
                                        self.src = URL.createObjectURL(stream);
                                    });
                                }
                            });
                        }
                    }
                },

                shimAddTrackRemoveTrackWithNative: function(window) {
                    // shim addTrack/removeTrack with native variants in order to make
                    // the interactions with legacy getLocalStreams behave as in other browsers.
                    // Keeps a mapping stream.id => [stream, rtpsenders...]
                    window.RTCPeerConnection.prototype.getLocalStreams = function() {
                        var pc = this;
                        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                        return Object.keys(this._shimmedLocalStreams).map(function(streamId) {
                            return pc._shimmedLocalStreams[streamId][0];
                        });
                    };

                    var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
                    window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                        if (!stream) {
                            return origAddTrack.apply(this, arguments);
                        }
                        this._shimmedLocalStreams = this._shimmedLocalStreams || {};

                        var sender = origAddTrack.apply(this, arguments);
                        if (!this._shimmedLocalStreams[stream.id]) {
                            this._shimmedLocalStreams[stream.id] = [stream, sender];
                        } else if (this._shimmedLocalStreams[stream.id].indexOf(sender) === -1) {
                            this._shimmedLocalStreams[stream.id].push(sender);
                        }
                        return sender;
                    };

                    var origAddStream = window.RTCPeerConnection.prototype.addStream;
                    window.RTCPeerConnection.prototype.addStream = function(stream) {
                        var pc = this;
                        this._shimmedLocalStreams = this._shimmedLocalStreams || {};

                        stream.getTracks().forEach(function(track) {
                            var alreadyExists = pc.getSenders().find(function(s) {
                                return s.track === track;
                            });
                            if (alreadyExists) {
                                throw new DOMException('Track already exists.',
                                    'InvalidAccessError');
                            }
                        });
                        var existingSenders = pc.getSenders();
                        origAddStream.apply(this, arguments);
                        var newSenders = pc.getSenders().filter(function(newSender) {
                            return existingSenders.indexOf(newSender) === -1;
                        });
                        this._shimmedLocalStreams[stream.id] = [stream].concat(newSenders);
                    };

                    var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
                    window.RTCPeerConnection.prototype.removeStream = function(stream) {
                        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                        delete this._shimmedLocalStreams[stream.id];
                        return origRemoveStream.apply(this, arguments);
                    };

                    var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
                    window.RTCPeerConnection.prototype.removeTrack = function(sender) {
                        var pc = this;
                        this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                        if (sender) {
                            Object.keys(this._shimmedLocalStreams).forEach(function(streamId) {
                                var idx = pc._shimmedLocalStreams[streamId].indexOf(sender);
                                if (idx !== -1) {
                                    pc._shimmedLocalStreams[streamId].splice(idx, 1);
                                }
                                if (pc._shimmedLocalStreams[streamId].length === 1) {
                                    delete pc._shimmedLocalStreams[streamId];
                                }
                            });
                        }
                        return origRemoveTrack.apply(this, arguments);
                    };
                },

                shimAddTrackRemoveTrack: function(window) {
                    var browserDetails = utils.detectBrowser(window);
                    // shim addTrack and removeTrack.
                    if (window.RTCPeerConnection.prototype.addTrack &&
                        browserDetails.version >= 65) {
                        return this.shimAddTrackRemoveTrackWithNative(window);
                    }

                    // also shim pc.getLocalStreams when addTrack is shimmed
                    // to return the original streams.
                    var origGetLocalStreams = window.RTCPeerConnection.prototype
                        .getLocalStreams;
                    window.RTCPeerConnection.prototype.getLocalStreams = function() {
                        var pc = this;
                        var nativeStreams = origGetLocalStreams.apply(this);
                        pc._reverseStreams = pc._reverseStreams || {};
                        return nativeStreams.map(function(stream) {
                            return pc._reverseStreams[stream.id];
                        });
                    };

                    var origAddStream = window.RTCPeerConnection.prototype.addStream;
                    window.RTCPeerConnection.prototype.addStream = function(stream) {
                        var pc = this;
                        pc._streams = pc._streams || {};
                        pc._reverseStreams = pc._reverseStreams || {};

                        stream.getTracks().forEach(function(track) {
                            var alreadyExists = pc.getSenders().find(function(s) {
                                return s.track === track;
                            });
                            if (alreadyExists) {
                                throw new DOMException('Track already exists.',
                                    'InvalidAccessError');
                            }
                        });
                        // Add identity mapping for consistency with addTrack.
                        // Unless this is being used with a stream from addTrack.
                        if (!pc._reverseStreams[stream.id]) {
                            var newStream = new window.MediaStream(stream.getTracks());
                            pc._streams[stream.id] = newStream;
                            pc._reverseStreams[newStream.id] = stream;
                            stream = newStream;
                        }
                        origAddStream.apply(pc, [stream]);
                    };

                    var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
                    window.RTCPeerConnection.prototype.removeStream = function(stream) {
                        var pc = this;
                        pc._streams = pc._streams || {};
                        pc._reverseStreams = pc._reverseStreams || {};

                        origRemoveStream.apply(pc, [(pc._streams[stream.id] || stream)]);
                        delete pc._reverseStreams[(pc._streams[stream.id] ?
                            pc._streams[stream.id].id : stream.id)];
                        delete pc._streams[stream.id];
                    };

                    window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                        var pc = this;
                        if (pc.signalingState === 'closed') {
                            throw new DOMException(
                                'The RTCPeerConnection\'s signalingState is \'closed\'.',
                                'InvalidStateError');
                        }
                        var streams = [].slice.call(arguments, 1);
                        if (streams.length !== 1 ||
                            !streams[0].getTracks().find(function(t) {
                                return t === track;
                            })) {
                            // this is not fully correct but all we can manage without
                            // [[associated MediaStreams]] internal slot.
                            throw new DOMException(
                                'The adapter.js addTrack polyfill only supports a single ' +
                                ' stream which is associated with the specified track.',
                                'NotSupportedError');
                        }

                        var alreadyExists = pc.getSenders().find(function(s) {
                            return s.track === track;
                        });
                        if (alreadyExists) {
                            throw new DOMException('Track already exists.',
                                'InvalidAccessError');
                        }

                        pc._streams = pc._streams || {};
                        pc._reverseStreams = pc._reverseStreams || {};
                        var oldStream = pc._streams[stream.id];
                        if (oldStream) {
                            // this is using odd Chrome behaviour, use with caution:
                            // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
                            // Note: we rely on the high-level addTrack/dtmf shim to
                            // create the sender with a dtmf sender.
                            oldStream.addTrack(track);

                            // Trigger ONN async.
                            Promise.resolve().then(function() {
                                pc.dispatchEvent(new Event('negotiationneeded'));
                            });
                        } else {
                            var newStream = new window.MediaStream([track]);
                            pc._streams[stream.id] = newStream;
                            pc._reverseStreams[newStream.id] = stream;
                            pc.addStream(newStream);
                        }
                        return pc.getSenders().find(function(s) {
                            return s.track === track;
                        });
                    };

                    // replace the internal stream id with the external one and
                    // vice versa.
                    function replaceInternalStreamId(pc, description) {
                        var sdp = description.sdp;
                        Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
                            var externalStream = pc._reverseStreams[internalId];
                            var internalStream = pc._streams[externalStream.id];
                            sdp = sdp.replace(new RegExp(internalStream.id, 'g'),
                                externalStream.id);
                        });
                        return new RTCSessionDescription({
                            type: description.type,
                            sdp: sdp
                        });
                    }

                    function replaceExternalStreamId(pc, description) {
                        var sdp = description.sdp;
                        Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
                            var externalStream = pc._reverseStreams[internalId];
                            var internalStream = pc._streams[externalStream.id];
                            sdp = sdp.replace(new RegExp(externalStream.id, 'g'),
                                internalStream.id);
                        });
                        return new RTCSessionDescription({
                            type: description.type,
                            sdp: sdp
                        });
                    }
                    ['createOffer', 'createAnswer'].forEach(function(method) {
                        var nativeMethod = window.RTCPeerConnection.prototype[method];
                        window.RTCPeerConnection.prototype[method] = function() {
                            var pc = this;
                            var args = arguments;
                            var isLegacyCall = arguments.length &&
                                typeof arguments[0] === 'function';
                            if (isLegacyCall) {
                                return nativeMethod.apply(pc, [
                                    function(description) {
                                        var desc = replaceInternalStreamId(pc, description);
                                        args[0].apply(null, [desc]);
                                    },
                                    function(err) {
                                        if (args[1]) {
                                            args[1].apply(null, err);
                                        }
                                    },
                                    arguments[2]
                                ]);
                            }
                            return nativeMethod.apply(pc, arguments)
                                .then(function(description) {
                                    return replaceInternalStreamId(pc, description);
                                });
                        };
                    });

                    var origSetLocalDescription =
                        window.RTCPeerConnection.prototype.setLocalDescription;
                    window.RTCPeerConnection.prototype.setLocalDescription = function() {
                        var pc = this;
                        if (!arguments.length || !arguments[0].type) {
                            return origSetLocalDescription.apply(pc, arguments);
                        }
                        arguments[0] = replaceExternalStreamId(pc, arguments[0]);
                        return origSetLocalDescription.apply(pc, arguments);
                    };

                    // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier

                    var origLocalDescription = Object.getOwnPropertyDescriptor(
                        window.RTCPeerConnection.prototype, 'localDescription');
                    Object.defineProperty(window.RTCPeerConnection.prototype,
                        'localDescription', {
                            get: function() {
                                var pc = this;
                                var description = origLocalDescription.get.apply(this);
                                if (description.type === '') {
                                    return description;
                                }
                                return replaceInternalStreamId(pc, description);
                            }
                        });

                    window.RTCPeerConnection.prototype.removeTrack = function(sender) {
                        var pc = this;
                        if (pc.signalingState === 'closed') {
                            throw new DOMException(
                                'The RTCPeerConnection\'s signalingState is \'closed\'.',
                                'InvalidStateError');
                        }
                        // We can not yet check for sender instanceof RTCRtpSender
                        // since we shim RTPSender. So we check if sender._pc is set.
                        if (!sender._pc) {
                            throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' +
                                'does not implement interface RTCRtpSender.', 'TypeError');
                        }
                        var isLocal = sender._pc === pc;
                        if (!isLocal) {
                            throw new DOMException('Sender was not created by this connection.',
                                'InvalidAccessError');
                        }

                        // Search for the native stream the senders track belongs to.
                        pc._streams = pc._streams || {};
                        var stream;
                        Object.keys(pc._streams).forEach(function(streamid) {
                            var hasTrack = pc._streams[streamid].getTracks().find(function(track) {
                                return sender.track === track;
                            });
                            if (hasTrack) {
                                stream = pc._streams[streamid];
                            }
                        });

                        if (stream) {
                            if (stream.getTracks().length === 1) {
                                // if this is the last track of the stream, remove the stream. This
                                // takes care of any shimmed _senders.
                                pc.removeStream(pc._reverseStreams[stream.id]);
                            } else {
                                // relying on the same odd chrome behaviour as above.
                                stream.removeTrack(sender.track);
                            }
                            pc.dispatchEvent(new Event('negotiationneeded'));
                        }
                    };
                },

                shimPeerConnection: function(window) {
                    var browserDetails = utils.detectBrowser(window);

                    // The RTCPeerConnection object.
                    if (!window.RTCPeerConnection && window.webkitRTCPeerConnection) {
                        window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                            // Translate iceTransportPolicy to iceTransports,
                            // see https://code.google.com/p/webrtc/issues/detail?id=4869
                            // this was fixed in M56 along with unprefixing RTCPeerConnection.
                            logging('PeerConnection');
                            if (pcConfig && pcConfig.iceTransportPolicy) {
                                pcConfig.iceTransports = pcConfig.iceTransportPolicy;
                            }

                            return new window.webkitRTCPeerConnection(pcConfig, pcConstraints);
                        };
                        window.RTCPeerConnection.prototype =
                            window.webkitRTCPeerConnection.prototype;
                        // wrap static methods. Currently just generateCertificate.
                        if (window.webkitRTCPeerConnection.generateCertificate) {
                            Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                                get: function() {
                                    return window.webkitRTCPeerConnection.generateCertificate;
                                }
                            });
                        }
                    } else {
                        // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
                        var OrigPeerConnection = window.RTCPeerConnection;
                        window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                            if (pcConfig && pcConfig.iceServers) {
                                var newIceServers = [];
                                for (var i = 0; i < pcConfig.iceServers.length; i++) {
                                    var server = pcConfig.iceServers[i];
                                    if (!server.hasOwnProperty('urls') &&
                                        server.hasOwnProperty('url')) {
                                        utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                                        server = JSON.parse(JSON.stringify(server));
                                        server.urls = server.url;
                                        newIceServers.push(server);
                                    } else {
                                        newIceServers.push(pcConfig.iceServers[i]);
                                    }
                                }
                                pcConfig.iceServers = newIceServers;
                            }
                            return new OrigPeerConnection(pcConfig, pcConstraints);
                        };
                        window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
                        // wrap static methods. Currently just generateCertificate.
                        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                            get: function() {
                                return OrigPeerConnection.generateCertificate;
                            }
                        });
                    }

                    var origGetStats = window.RTCPeerConnection.prototype.getStats;
                    window.RTCPeerConnection.prototype.getStats = function(selector,
                        successCallback, errorCallback) {
                        var pc = this;
                        var args = arguments;

                        // If selector is a function then we are in the old style stats so just
                        // pass back the original getStats format to avoid breaking old users.
                        if (arguments.length > 0 && typeof selector === 'function') {
                            return origGetStats.apply(this, arguments);
                        }

                        // When spec-style getStats is supported, return those when called with
                        // either no arguments or the selector argument is null.
                        if (origGetStats.length === 0 && (arguments.length === 0 ||
                                typeof arguments[0] !== 'function')) {
                            return origGetStats.apply(this, []);
                        }

                        var fixChromeStats_ = function(response) {
                            var standardReport = {};
                            var reports = response.result();
                            reports.forEach(function(report) {
                                var standardStats = {
                                    id: report.id,
                                    timestamp: report.timestamp,
                                    type: {
                                        localcandidate: 'local-candidate',
                                        remotecandidate: 'remote-candidate'
                                    }[report.type] || report.type
                                };
                                report.names().forEach(function(name) {
                                    standardStats[name] = report.stat(name);
                                });
                                standardReport[standardStats.id] = standardStats;
                            });

                            return standardReport;
                        };

                        // shim getStats with maplike support
                        var makeMapStats = function(stats) {
                            return new Map(Object.keys(stats).map(function(key) {
                                return [key, stats[key]];
                            }));
                        };

                        if (arguments.length >= 2) {
                            var successCallbackWrapper_ = function(response) {
                                args[1](makeMapStats(fixChromeStats_(response)));
                            };

                            return origGetStats.apply(this, [successCallbackWrapper_,
                                arguments[0]
                            ]);
                        }

                        // promise-support
                        return new Promise(function(resolve, reject) {
                            origGetStats.apply(pc, [
                                function(response) {
                                    resolve(makeMapStats(fixChromeStats_(response)));
                                },
                                reject
                            ]);
                        }).then(successCallback, errorCallback);
                    };

                    // add promise support -- natively available in Chrome 51
                    if (browserDetails.version < 51) {
                        ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
                        .forEach(function(method) {
                            var nativeMethod = window.RTCPeerConnection.prototype[method];
                            window.RTCPeerConnection.prototype[method] = function() {
                                var args = arguments;
                                var pc = this;
                                var promise = new Promise(function(resolve, reject) {
                                    nativeMethod.apply(pc, [args[0], resolve, reject]);
                                });
                                if (args.length < 2) {
                                    return promise;
                                }
                                return promise.then(function() {
                                        args[1].apply(null, []);
                                    },
                                    function(err) {
                                        if (args.length >= 3) {
                                            args[2].apply(null, [err]);
                                        }
                                    });
                            };
                        });
                    }

                    // promise support for createOffer and createAnswer. Available (without
                    // bugs) since M52: crbug/619289
                    if (browserDetails.version < 52) {
                        ['createOffer', 'createAnswer'].forEach(function(method) {
                            var nativeMethod = window.RTCPeerConnection.prototype[method];
                            window.RTCPeerConnection.prototype[method] = function() {
                                var pc = this;
                                if (arguments.length < 1 || (arguments.length === 1 &&
                                        typeof arguments[0] === 'object')) {
                                    var opts = arguments.length === 1 ? arguments[0] : undefined;
                                    return new Promise(function(resolve, reject) {
                                        nativeMethod.apply(pc, [resolve, reject, opts]);
                                    });
                                }
                                return nativeMethod.apply(this, arguments);
                            };
                        });
                    }

                    // shim implicit creation of RTCSessionDescription/RTCIceCandidate
                    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
                    .forEach(function(method) {
                        var nativeMethod = window.RTCPeerConnection.prototype[method];
                        window.RTCPeerConnection.prototype[method] = function() {
                            arguments[0] = new((method === 'addIceCandidate') ?
                                window.RTCIceCandidate :
                                window.RTCSessionDescription)(arguments[0]);
                            return nativeMethod.apply(this, arguments);
                        };
                    });

                    // support for addIceCandidate(null or undefined)
                    var nativeAddIceCandidate =
                        window.RTCPeerConnection.prototype.addIceCandidate;
                    window.RTCPeerConnection.prototype.addIceCandidate = function() {
                        if (!arguments[0]) {
                            if (arguments[1]) {
                                arguments[1].apply(null);
                            }
                            return Promise.resolve();
                        }
                        return nativeAddIceCandidate.apply(this, arguments);
                    };
                }
            };

        }, {
            "../utils.js": 13,
            "./getusermedia": 6
        }],
        6: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';
            var utils = require('../utils.js');
            var logging = utils.log;

            // Expose public methods.
            module.exports = function(window) {
                var browserDetails = utils.detectBrowser(window);
                var navigator = window && window.navigator;

                var constraintsToChrome_ = function(c) {
                    if (typeof c !== 'object' || c.mandatory || c.optional) {
                        return c;
                    }
                    var cc = {};
                    Object.keys(c).forEach(function(key) {
                        if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
                            return;
                        }
                        var r = (typeof c[key] === 'object') ? c[key] : {
                            ideal: c[key]
                        };
                        if (r.exact !== undefined && typeof r.exact === 'number') {
                            r.min = r.max = r.exact;
                        }
                        var oldname_ = function(prefix, name) {
                            if (prefix) {
                                return prefix + name.charAt(0).toUpperCase() + name.slice(1);
                            }
                            return (name === 'deviceId') ? 'sourceId' : name;
                        };
                        if (r.ideal !== undefined) {
                            cc.optional = cc.optional || [];
                            var oc = {};
                            if (typeof r.ideal === 'number') {
                                oc[oldname_('min', key)] = r.ideal;
                                cc.optional.push(oc);
                                oc = {};
                                oc[oldname_('max', key)] = r.ideal;
                                cc.optional.push(oc);
                            } else {
                                oc[oldname_('', key)] = r.ideal;
                                cc.optional.push(oc);
                            }
                        }
                        if (r.exact !== undefined && typeof r.exact !== 'number') {
                            cc.mandatory = cc.mandatory || {};
                            cc.mandatory[oldname_('', key)] = r.exact;
                        } else {
                            ['min', 'max'].forEach(function(mix) {
                                if (r[mix] !== undefined) {
                                    cc.mandatory = cc.mandatory || {};
                                    cc.mandatory[oldname_(mix, key)] = r[mix];
                                }
                            });
                        }
                    });
                    if (c.advanced) {
                        cc.optional = (cc.optional || []).concat(c.advanced);
                    }
                    return cc;
                };

                var shimConstraints_ = function(constraints, func) {
                    if (browserDetails.version >= 61) {
                        return func(constraints);
                    }
                    constraints = JSON.parse(JSON.stringify(constraints));
                    if (constraints && typeof constraints.audio === 'object') {
                        var remap = function(obj, a, b) {
                            if (a in obj && !(b in obj)) {
                                obj[b] = obj[a];
                                delete obj[a];
                            }
                        };
                        constraints = JSON.parse(JSON.stringify(constraints));
                        remap(constraints.audio, 'autoGainControl', 'googAutoGainControl');
                        remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression');
                        constraints.audio = constraintsToChrome_(constraints.audio);
                    }
                    if (constraints && typeof constraints.video === 'object') {
                        // Shim facingMode for mobile & surface pro.
                        var face = constraints.video.facingMode;
                        face = face && ((typeof face === 'object') ? face : {
                            ideal: face
                        });
                        var getSupportedFacingModeLies = browserDetails.version < 66;

                        if ((face && (face.exact === 'user' || face.exact === 'environment' ||
                                face.ideal === 'user' || face.ideal === 'environment')) &&
                            !(navigator.mediaDevices.getSupportedConstraints &&
                                navigator.mediaDevices.getSupportedConstraints().facingMode &&
                                !getSupportedFacingModeLies)) {
                            delete constraints.video.facingMode;
                            var matches;
                            if (face.exact === 'environment' || face.ideal === 'environment') {
                                matches = ['back', 'rear'];
                            } else if (face.exact === 'user' || face.ideal === 'user') {
                                matches = ['front'];
                            }
                            if (matches) {
                                // Look for matches in label, or use last cam for back (typical).
                                return navigator.mediaDevices.enumerateDevices()
                                    .then(function(devices) {
                                        devices = devices.filter(function(d) {
                                            return d.kind === 'videoinput';
                                        });
                                        var dev = devices.find(function(d) {
                                            return matches.some(function(match) {
                                                return d.label.toLowerCase().indexOf(match) !== -1;
                                            });
                                        });
                                        if (!dev && devices.length && matches.indexOf('back') !== -1) {
                                            dev = devices[devices.length - 1]; // more likely the back cam
                                        }
                                        if (dev) {
                                            constraints.video.deviceId = face.exact ? {
                                                exact: dev.deviceId
                                            } : {
                                                ideal: dev.deviceId
                                            };
                                        }
                                        constraints.video = constraintsToChrome_(constraints.video);
                                        logging('chrome: ' + JSON.stringify(constraints));
                                        return func(constraints);
                                    });
                            }
                        }
                        constraints.video = constraintsToChrome_(constraints.video);
                    }
                    logging('chrome: ' + JSON.stringify(constraints));
                    return func(constraints);
                };

                var shimError_ = function(e) {
                    return {
                        name: {
                            PermissionDeniedError: 'NotAllowedError',
                            PermissionDismissedError: 'NotAllowedError',
                            InvalidStateError: 'NotAllowedError',
                            DevicesNotFoundError: 'NotFoundError',
                            ConstraintNotSatisfiedError: 'OverconstrainedError',
                            TrackStartError: 'NotReadableError',
                            MediaDeviceFailedDueToShutdown: 'NotAllowedError',
                            MediaDeviceKillSwitchOn: 'NotAllowedError',
                            TabCaptureError: 'AbortError',
                            ScreenCaptureError: 'AbortError',
                            DeviceCaptureError: 'AbortError'
                        }[e.name] || e.name,
                        message: e.message,
                        constraint: e.constraintName,
                        toString: function() {
                            return this.name + (this.message && ': ') + this.message;
                        }
                    };
                };

                var getUserMedia_ = function(constraints, onSuccess, onError) {
                    shimConstraints_(constraints, function(c) {
                        navigator.webkitGetUserMedia(c, onSuccess, function(e) {
                            if (onError) {
                                onError(shimError_(e));
                            }
                        });
                    });
                };

                navigator.getUserMedia = getUserMedia_;

                // Returns the result of getUserMedia as a Promise.
                var getUserMediaPromise_ = function(constraints) {
                    return new Promise(function(resolve, reject) {
                        navigator.getUserMedia(constraints, resolve, reject);
                    });
                };

                if (!navigator.mediaDevices) {
                    navigator.mediaDevices = {
                        getUserMedia: getUserMediaPromise_,
                        enumerateDevices: function() {
                            return new Promise(function(resolve) {
                                var kinds = {
                                    audio: 'audioinput',
                                    video: 'videoinput'
                                };
                                return window.MediaStreamTrack.getSources(function(devices) {
                                    resolve(devices.map(function(device) {
                                        return {
                                            label: device.label,
                                            kind: kinds[device.kind],
                                            deviceId: device.id,
                                            groupId: ''
                                        };
                                    }));
                                });
                            });
                        },
                        getSupportedConstraints: function() {
                            return {
                                deviceId: true,
                                echoCancellation: true,
                                facingMode: true,
                                frameRate: true,
                                height: true,
                                width: true
                            };
                        }
                    };
                }

                // A shim for getUserMedia method on the mediaDevices object.
                // TODO(KaptenJansson) remove once implemented in Chrome stable.
                if (!navigator.mediaDevices.getUserMedia) {
                    navigator.mediaDevices.getUserMedia = function(constraints) {
                        return getUserMediaPromise_(constraints);
                    };
                } else {
                    // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
                    // function which returns a Promise, it does not accept spec-style
                    // constraints.
                    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
                    bind(navigator.mediaDevices);
                    navigator.mediaDevices.getUserMedia = function(cs) {
                        return shimConstraints_(cs, function(c) {
                            return origGetUserMedia(c).then(function(stream) {
                                if (c.audio && !stream.getAudioTracks().length ||
                                    c.video && !stream.getVideoTracks().length) {
                                    stream.getTracks().forEach(function(track) {
                                        track.stop();
                                    });
                                    throw new DOMException('', 'NotFoundError');
                                }
                                return stream;
                            }, function(e) {
                                return Promise.reject(shimError_(e));
                            });
                        });
                    };
                }

                // Dummy devicechange event methods.
                // TODO(KaptenJansson) remove once implemented in Chrome stable.
                if (typeof navigator.mediaDevices.addEventListener === 'undefined') {
                    navigator.mediaDevices.addEventListener = function() {
                        logging('Dummy mediaDevices.addEventListener called.');
                    };
                }
                if (typeof navigator.mediaDevices.removeEventListener === 'undefined') {
                    navigator.mediaDevices.removeEventListener = function() {
                        logging('Dummy mediaDevices.removeEventListener called.');
                    };
                }
            };

        }, {
            "../utils.js": 13
        }],
        7: [function(require, module, exports) {
            /*
             *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            var SDPUtils = require('sdp');
            var utils = require('./utils');

            module.exports = {
                shimRTCIceCandidate: function(window) {
                    // foundation is arbitrarily chosen as an indicator for full support for
                    // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
                    if (!window.RTCIceCandidate || (window.RTCIceCandidate && 'foundation' in
                            window.RTCIceCandidate.prototype)) {
                        return;
                    }

                    var NativeRTCIceCandidate = window.RTCIceCandidate;
                    window.RTCIceCandidate = function(args) {
                        // Remove the a= which shouldn't be part of the candidate string.
                        if (typeof args === 'object' && args.candidate &&
                            args.candidate.indexOf('a=') === 0) {
                            args = JSON.parse(JSON.stringify(args));
                            args.candidate = args.candidate.substr(2);
                        }

                        if (args.candidate && args.candidate.length) {
                            // Augment the native candidate with the parsed fields.
                            var nativeCandidate = new NativeRTCIceCandidate(args);
                            var parsedCandidate = SDPUtils.parseCandidate(args.candidate);
                            var augmentedCandidate = Object.assign(nativeCandidate,
                                parsedCandidate);

                            // Add a serializer that does not serialize the extra attributes.
                            augmentedCandidate.toJSON = function() {
                                return {
                                    candidate: augmentedCandidate.candidate,
                                    sdpMid: augmentedCandidate.sdpMid,
                                    sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
                                    usernameFragment: augmentedCandidate.usernameFragment,
                                };
                            };
                            return augmentedCandidate;
                        }
                        return new NativeRTCIceCandidate(args);
                    };
                    window.RTCIceCandidate.prototype = NativeRTCIceCandidate.prototype;

                    // Hook up the augmented candidate in onicecandidate and
                    // addEventListener('icecandidate', ...)
                    utils.wrapPeerConnectionEvent(window, 'icecandidate', function(e) {
                        if (e.candidate) {
                            Object.defineProperty(e, 'candidate', {
                                value: new window.RTCIceCandidate(e.candidate),
                                writable: 'false'
                            });
                        }
                        return e;
                    });
                },

                // shimCreateObjectURL must be called before shimSourceObject to avoid loop.

                shimCreateObjectURL: function(window) {
                    var URL = window && window.URL;

                    if (!(typeof window === 'object' && window.HTMLMediaElement &&
                            'srcObject' in window.HTMLMediaElement.prototype &&
                            URL.createObjectURL && URL.revokeObjectURL)) {
                        // Only shim CreateObjectURL using srcObject if srcObject exists.
                        return undefined;
                    }

                    var nativeCreateObjectURL = URL.createObjectURL.bind(URL);
                    var nativeRevokeObjectURL = URL.revokeObjectURL.bind(URL);
                    var streams = new Map(),
                        newId = 0;

                    URL.createObjectURL = function(stream) {
                        if ('getTracks' in stream) {
                            var url = 'polyblob:' + (++newId);
                            streams.set(url, stream);
                            utils.deprecated('URL.createObjectURL(stream)',
                                'elem.srcObject = stream');
                            return url;
                        }
                        return nativeCreateObjectURL(stream);
                    };
                    URL.revokeObjectURL = function(url) {
                        nativeRevokeObjectURL(url);
                        streams.delete(url);
                    };

                    var dsc = Object.getOwnPropertyDescriptor(window.HTMLMediaElement.prototype,
                        'src');
                    Object.defineProperty(window.HTMLMediaElement.prototype, 'src', {
                        get: function() {
                            return dsc.get.apply(this);
                        },
                        set: function(url) {
                            this.srcObject = streams.get(url) || null;
                            return dsc.set.apply(this, [url]);
                        }
                    });

                    var nativeSetAttribute = window.HTMLMediaElement.prototype.setAttribute;
                    window.HTMLMediaElement.prototype.setAttribute = function() {
                        if (arguments.length === 2 &&
                            ('' + arguments[0]).toLowerCase() === 'src') {
                            this.srcObject = streams.get(arguments[1]) || null;
                        }
                        return nativeSetAttribute.apply(this, arguments);
                    };
                },

                shimMaxMessageSize: function(window) {
                    if (window.RTCSctpTransport || !window.RTCPeerConnection) {
                        return;
                    }
                    var browserDetails = utils.detectBrowser(window);

                    if (!('sctp' in window.RTCPeerConnection.prototype)) {
                        Object.defineProperty(window.RTCPeerConnection.prototype, 'sctp', {
                            get: function() {
                                return typeof this._sctp === 'undefined' ? null : this._sctp;
                            }
                        });
                    }

                    var sctpInDescription = function(description) {
                        var sections = SDPUtils.splitSections(description.sdp);
                        sections.shift();
                        return sections.some(function(mediaSection) {
                            var mLine = SDPUtils.parseMLine(mediaSection);
                            return mLine && mLine.kind === 'application' &&
                                mLine.protocol.indexOf('SCTP') !== -1;
                        });
                    };

                    var getRemoteFirefoxVersion = function(description) {
                        // TODO: Is there a better solution for detecting Firefox?
                        var match = description.sdp.match(/mozilla...THIS_IS_SDPARTA-(\d+)/);
                        if (match === null || match.length < 2) {
                            return -1;
                        }
                        var version = parseInt(match[1], 10);
                        // Test for NaN (yes, this is ugly)
                        return version !== version ? -1 : version;
                    };

                    var getCanSendMaxMessageSize = function(remoteIsFirefox) {
                        // Every implementation we know can send at least 64 KiB.
                        // Note: Although Chrome is technically able to send up to 256 KiB, the
                        //       data does not reach the other peer reliably.
                        //       See: https://bugs.chromium.org/p/webrtc/issues/detail?id=8419
                        var canSendMaxMessageSize = 65536;
                        if (browserDetails.browser === 'firefox') {
                            if (browserDetails.version < 57) {
                                if (remoteIsFirefox === -1) {
                                    // FF < 57 will send in 16 KiB chunks using the deprecated PPID
                                    // fragmentation.
                                    canSendMaxMessageSize = 16384;
                                } else {
                                    // However, other FF (and RAWRTC) can reassemble PPID-fragmented
                                    // messages. Thus, supporting ~2 GiB when sending.
                                    canSendMaxMessageSize = 2147483637;
                                }
                            } else {
                                // Currently, all FF >= 57 will reset the remote maximum message size
                                // to the default value when a data channel is created at a later
                                // stage. :(
                                // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
                                canSendMaxMessageSize =
                                    browserDetails.version === 57 ? 65535 : 65536;
                            }
                        }
                        return canSendMaxMessageSize;
                    };

                    var getMaxMessageSize = function(description, remoteIsFirefox) {
                        // Note: 65536 bytes is the default value from the SDP spec. Also,
                        //       every implementation we know supports receiving 65536 bytes.
                        var maxMessageSize = 65536;

                        // FF 57 has a slightly incorrect default remote max message size, so
                        // we need to adjust it here to avoid a failure when sending.
                        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1425697
                        if (browserDetails.browser === 'firefox' &&
                            browserDetails.version === 57) {
                            maxMessageSize = 65535;
                        }

                        var match = SDPUtils.matchPrefix(description.sdp, 'a=max-message-size:');
                        if (match.length > 0) {
                            maxMessageSize = parseInt(match[0].substr(19), 10);
                        } else if (browserDetails.browser === 'firefox' &&
                            remoteIsFirefox !== -1) {
                            // If the maximum message size is not present in the remote SDP and
                            // both local and remote are Firefox, the remote peer can receive
                            // ~2 GiB.
                            maxMessageSize = 2147483637;
                        }
                        return maxMessageSize;
                    };

                    var origSetRemoteDescription =
                        window.RTCPeerConnection.prototype.setRemoteDescription;
                    window.RTCPeerConnection.prototype.setRemoteDescription = function() {
                        var pc = this;
                        pc._sctp = null;

                        if (sctpInDescription(arguments[0])) {
                            // Check if the remote is FF.
                            var isFirefox = getRemoteFirefoxVersion(arguments[0]);

                            // Get the maximum message size the local peer is capable of sending
                            var canSendMMS = getCanSendMaxMessageSize(isFirefox);

                            // Get the maximum message size of the remote peer.
                            var remoteMMS = getMaxMessageSize(arguments[0], isFirefox);

                            // Determine final maximum message size
                            var maxMessageSize;
                            if (canSendMMS === 0 && remoteMMS === 0) {
                                maxMessageSize = Number.POSITIVE_INFINITY;
                            } else if (canSendMMS === 0 || remoteMMS === 0) {
                                maxMessageSize = Math.max(canSendMMS, remoteMMS);
                            } else {
                                maxMessageSize = Math.min(canSendMMS, remoteMMS);
                            }

                            // Create a dummy RTCSctpTransport object and the 'maxMessageSize'
                            // attribute.
                            var sctp = {};
                            Object.defineProperty(sctp, 'maxMessageSize', {
                                get: function() {
                                    return maxMessageSize;
                                }
                            });
                            pc._sctp = sctp;
                        }

                        return origSetRemoteDescription.apply(pc, arguments);
                    };
                },

                shimSendThrowTypeError: function(window) {
                    if (!(window.RTCPeerConnection &&
                            'createDataChannel' in window.RTCPeerConnection.prototype)) {
                        return;
                    }

                    // Note: Although Firefox >= 57 has a native implementation, the maximum
                    //       message size can be reset for all data channels at a later stage.
                    //       See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831

                    var origCreateDataChannel =
                        window.RTCPeerConnection.prototype.createDataChannel;
                    window.RTCPeerConnection.prototype.createDataChannel = function() {
                        var pc = this;
                        var dataChannel = origCreateDataChannel.apply(pc, arguments);
                        var origDataChannelSend = dataChannel.send;

                        // Patch 'send' method
                        dataChannel.send = function() {
                            var dc = this;
                            var data = arguments[0];
                            var length = data.length || data.size || data.byteLength;
                            if (length > pc.sctp.maxMessageSize) {
                                throw new DOMException('Message too large (can send a maximum of ' +
                                    pc.sctp.maxMessageSize + ' bytes)', 'TypeError');
                            }
                            return origDataChannelSend.apply(dc, arguments);
                        };

                        return dataChannel;
                    };
                }
            };

        }, {
            "./utils": 13,
            "sdp": 2
        }],
        8: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            var utils = require('../utils');
            var shimRTCPeerConnection = require('rtcpeerconnection-shim');

            module.exports = {
                shimGetUserMedia: require('./getusermedia'),
                shimPeerConnection: function(window) {
                    var browserDetails = utils.detectBrowser(window);

                    if (window.RTCIceGatherer) {
                        if (!window.RTCIceCandidate) {
                            window.RTCIceCandidate = function(args) {
                                return args;
                            };
                        }
                        if (!window.RTCSessionDescription) {
                            window.RTCSessionDescription = function(args) {
                                return args;
                            };
                        }
                        // this adds an additional event listener to MediaStrackTrack that signals
                        // when a tracks enabled property was changed. Workaround for a bug in
                        // addStream, see below. No longer required in 15025+
                        if (browserDetails.version < 15025) {
                            var origMSTEnabled = Object.getOwnPropertyDescriptor(
                                window.MediaStreamTrack.prototype, 'enabled');
                            Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
                                set: function(value) {
                                    origMSTEnabled.set.call(this, value);
                                    var ev = new Event('enabled');
                                    ev.enabled = value;
                                    this.dispatchEvent(ev);
                                }
                            });
                        }
                    }

                    // ORTC defines the DTMF sender a bit different.
                    // https://github.com/w3c/ortc/issues/714
                    if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
                        Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
                            get: function() {
                                if (this._dtmf === undefined) {
                                    if (this.track.kind === 'audio') {
                                        this._dtmf = new window.RTCDtmfSender(this);
                                    } else if (this.track.kind === 'video') {
                                        this._dtmf = null;
                                    }
                                }
                                return this._dtmf;
                            }
                        });
                    }
                    // Edge currently only implements the RTCDtmfSender, not the
                    // RTCDTMFSender alias. See http://draft.ortc.org/#rtcdtmfsender2*
                    if (window.RTCDtmfSender && !window.RTCDTMFSender) {
                        window.RTCDTMFSender = window.RTCDtmfSender;
                    }

                    window.RTCPeerConnection =
                        shimRTCPeerConnection(window, browserDetails.version);
                },
                shimReplaceTrack: function(window) {
                    // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
                    if (window.RTCRtpSender &&
                        !('replaceTrack' in window.RTCRtpSender.prototype)) {
                        window.RTCRtpSender.prototype.replaceTrack =
                            window.RTCRtpSender.prototype.setTrack;
                    }
                }
            };

        }, {
            "../utils": 13,
            "./getusermedia": 9,
            "rtcpeerconnection-shim": 1
        }],
        9: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            // Expose public methods.
            module.exports = function(window) {
                var navigator = window && window.navigator;

                var shimError_ = function(e) {
                    return {
                        name: {
                            PermissionDeniedError: 'NotAllowedError'
                        }[e.name] || e.name,
                        message: e.message,
                        constraint: e.constraint,
                        toString: function() {
                            return this.name;
                        }
                    };
                };

                // getUserMedia error shim.
                var origGetUserMedia = navigator.mediaDevices.getUserMedia.
                bind(navigator.mediaDevices);
                navigator.mediaDevices.getUserMedia = function(c) {
                    return origGetUserMedia(c).catch(function(e) {
                        return Promise.reject(shimError_(e));
                    });
                };
            };

        }, {}],
        10: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            var utils = require('../utils');

            module.exports = {
                shimGetUserMedia: require('./getusermedia'),
                shimOnTrack: function(window) {
                    if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
                            window.RTCPeerConnection.prototype)) {
                        Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
                            get: function() {
                                return this._ontrack;
                            },
                            set: function(f) {
                                if (this._ontrack) {
                                    this.removeEventListener('track', this._ontrack);
                                    this.removeEventListener('addstream', this._ontrackpoly);
                                }
                                this.addEventListener('track', this._ontrack = f);
                                this.addEventListener('addstream', this._ontrackpoly = function(e) {
                                    e.stream.getTracks().forEach(function(track) {
                                        var event = new Event('track');
                                        event.track = track;
                                        event.receiver = {
                                            track: track
                                        };
                                        event.transceiver = {
                                            receiver: event.receiver
                                        };
                                        event.streams = [e.stream];
                                        this.dispatchEvent(event);
                                    }.bind(this));
                                }.bind(this));
                            }
                        });
                    }
                    if (typeof window === 'object' && window.RTCTrackEvent &&
                        ('receiver' in window.RTCTrackEvent.prototype) &&
                        !('transceiver' in window.RTCTrackEvent.prototype)) {
                        Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
                            get: function() {
                                return {
                                    receiver: this.receiver
                                };
                            }
                        });
                    }
                },

                shimSourceObject: function(window) {
                    // Firefox has supported mozSrcObject since FF22, unprefixed in 42.
                    if (typeof window === 'object') {
                        if (window.HTMLMediaElement &&
                            !('srcObject' in window.HTMLMediaElement.prototype)) {
                            // Shim the srcObject property, once, when HTMLMediaElement is found.
                            Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
                                get: function() {
                                    return this.mozSrcObject;
                                },
                                set: function(stream) {
                                    this.mozSrcObject = stream;
                                }
                            });
                        }
                    }
                },

                shimPeerConnection: function(window) {
                    var browserDetails = utils.detectBrowser(window);

                    if (typeof window !== 'object' || !(window.RTCPeerConnection ||
                            window.mozRTCPeerConnection)) {
                        return; // probably media.peerconnection.enabled=false in about:config
                    }
                    // The RTCPeerConnection object.
                    if (!window.RTCPeerConnection) {
                        window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                            if (browserDetails.version < 38) {
                                // .urls is not supported in FF < 38.
                                // create RTCIceServers with a single url.
                                if (pcConfig && pcConfig.iceServers) {
                                    var newIceServers = [];
                                    for (var i = 0; i < pcConfig.iceServers.length; i++) {
                                        var server = pcConfig.iceServers[i];
                                        if (server.hasOwnProperty('urls')) {
                                            for (var j = 0; j < server.urls.length; j++) {
                                                var newServer = {
                                                    url: server.urls[j]
                                                };
                                                if (server.urls[j].indexOf('turn') === 0) {
                                                    newServer.username = server.username;
                                                    newServer.credential = server.credential;
                                                }
                                                newIceServers.push(newServer);
                                            }
                                        } else {
                                            newIceServers.push(pcConfig.iceServers[i]);
                                        }
                                    }
                                    pcConfig.iceServers = newIceServers;
                                }
                            }
                            return new window.mozRTCPeerConnection(pcConfig, pcConstraints);
                        };
                        window.RTCPeerConnection.prototype =
                            window.mozRTCPeerConnection.prototype;

                        // wrap static methods. Currently just generateCertificate.
                        if (window.mozRTCPeerConnection.generateCertificate) {
                            Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                                get: function() {
                                    return window.mozRTCPeerConnection.generateCertificate;
                                }
                            });
                        }

                        window.RTCSessionDescription = window.mozRTCSessionDescription;
                        window.RTCIceCandidate = window.mozRTCIceCandidate;
                    }

                    // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
                    ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
                    .forEach(function(method) {
                        var nativeMethod = window.RTCPeerConnection.prototype[method];
                        window.RTCPeerConnection.prototype[method] = function() {
                            arguments[0] = new((method === 'addIceCandidate') ?
                                window.RTCIceCandidate :
                                window.RTCSessionDescription)(arguments[0]);
                            return nativeMethod.apply(this, arguments);
                        };
                    });

                    // support for addIceCandidate(null or undefined)
                    var nativeAddIceCandidate =
                        window.RTCPeerConnection.prototype.addIceCandidate;
                    window.RTCPeerConnection.prototype.addIceCandidate = function() {
                        if (!arguments[0]) {
                            if (arguments[1]) {
                                arguments[1].apply(null);
                            }
                            return Promise.resolve();
                        }
                        return nativeAddIceCandidate.apply(this, arguments);
                    };

                    // shim getStats with maplike support
                    var makeMapStats = function(stats) {
                        var map = new Map();
                        Object.keys(stats).forEach(function(key) {
                            map.set(key, stats[key]);
                            map[key] = stats[key];
                        });
                        return map;
                    };

                    var modernStatsTypes = {
                        inboundrtp: 'inbound-rtp',
                        outboundrtp: 'outbound-rtp',
                        candidatepair: 'candidate-pair',
                        localcandidate: 'local-candidate',
                        remotecandidate: 'remote-candidate'
                    };

                    var nativeGetStats = window.RTCPeerConnection.prototype.getStats;
                    window.RTCPeerConnection.prototype.getStats = function(
                        selector,
                        onSucc,
                        onErr
                    ) {
                        return nativeGetStats.apply(this, [selector || null])
                            .then(function(stats) {
                                if (browserDetails.version < 48) {
                                    stats = makeMapStats(stats);
                                }
                                if (browserDetails.version < 53 && !onSucc) {
                                    // Shim only promise getStats with spec-hyphens in type names
                                    // Leave callback version alone; misc old uses of forEach before Map
                                    try {
                                        stats.forEach(function(stat) {
                                            stat.type = modernStatsTypes[stat.type] || stat.type;
                                        });
                                    } catch (e) {
                                        if (e.name !== 'TypeError') {
                                            throw e;
                                        }
                                        // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
                                        stats.forEach(function(stat, i) {
                                            stats.set(i, Object.assign({}, stat, {
                                                type: modernStatsTypes[stat.type] || stat.type
                                            }));
                                        });
                                    }
                                }
                                return stats;
                            })
                            .then(onSucc, onErr);
                    };
                },

                shimRemoveStream: function(window) {
                    if (!window.RTCPeerConnection ||
                        'removeStream' in window.RTCPeerConnection.prototype) {
                        return;
                    }
                    window.RTCPeerConnection.prototype.removeStream = function(stream) {
                        var pc = this;
                        utils.deprecated('removeStream', 'removeTrack');
                        this.getSenders().forEach(function(sender) {
                            if (sender.track && stream.getTracks().indexOf(sender.track) !== -1) {
                                pc.removeTrack(sender);
                            }
                        });
                    };
                }
            };

        }, {
            "../utils": 13,
            "./getusermedia": 11
        }],
        11: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            var utils = require('../utils');
            var logging = utils.log;

            // Expose public methods.
            module.exports = function(window) {
                var browserDetails = utils.detectBrowser(window);
                var navigator = window && window.navigator;
                var MediaStreamTrack = window && window.MediaStreamTrack;

                var shimError_ = function(e) {
                    return {
                        name: {
                            InternalError: 'NotReadableError',
                            NotSupportedError: 'TypeError',
                            PermissionDeniedError: 'NotAllowedError',
                            SecurityError: 'NotAllowedError'
                        }[e.name] || e.name,
                        message: {
                            'The operation is insecure.': 'The request is not allowed by the ' +
                                'user agent or the platform in the current context.'
                        }[e.message] || e.message,
                        constraint: e.constraint,
                        toString: function() {
                            return this.name + (this.message && ': ') + this.message;
                        }
                    };
                };

                // getUserMedia constraints shim.
                var getUserMedia_ = function(constraints, onSuccess, onError) {
                    var constraintsToFF37_ = function(c) {
                        if (typeof c !== 'object' || c.require) {
                            return c;
                        }
                        var require = [];
                        Object.keys(c).forEach(function(key) {
                            if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
                                return;
                            }
                            var r = c[key] = (typeof c[key] === 'object') ?
                                c[key] : {
                                    ideal: c[key]
                                };
                            if (r.min !== undefined ||
                                r.max !== undefined || r.exact !== undefined) {
                                require.push(key);
                            }
                            if (r.exact !== undefined) {
                                if (typeof r.exact === 'number') {
                                    r.min = r.max = r.exact;
                                } else {
                                    c[key] = r.exact;
                                }
                                delete r.exact;
                            }
                            if (r.ideal !== undefined) {
                                c.advanced = c.advanced || [];
                                var oc = {};
                                if (typeof r.ideal === 'number') {
                                    oc[key] = {
                                        min: r.ideal,
                                        max: r.ideal
                                    };
                                } else {
                                    oc[key] = r.ideal;
                                }
                                c.advanced.push(oc);
                                delete r.ideal;
                                if (!Object.keys(r).length) {
                                    delete c[key];
                                }
                            }
                        });
                        if (require.length) {
                            c.require = require;
                        }
                        return c;
                    };
                    constraints = JSON.parse(JSON.stringify(constraints));
                    if (browserDetails.version < 38) {
                        logging('spec: ' + JSON.stringify(constraints));
                        if (constraints.audio) {
                            constraints.audio = constraintsToFF37_(constraints.audio);
                        }
                        if (constraints.video) {
                            constraints.video = constraintsToFF37_(constraints.video);
                        }
                        logging('ff37: ' + JSON.stringify(constraints));
                    }
                    return navigator.mozGetUserMedia(constraints, onSuccess, function(e) {
                        onError(shimError_(e));
                    });
                };

                // Returns the result of getUserMedia as a Promise.
                var getUserMediaPromise_ = function(constraints) {
                    return new Promise(function(resolve, reject) {
                        getUserMedia_(constraints, resolve, reject);
                    });
                };

                // Shim for mediaDevices on older versions.
                if (!navigator.mediaDevices) {
                    navigator.mediaDevices = {
                        getUserMedia: getUserMediaPromise_,
                        addEventListener: function() {},
                        removeEventListener: function() {}
                    };
                }
                navigator.mediaDevices.enumerateDevices =
                    navigator.mediaDevices.enumerateDevices || function() {
                        return new Promise(function(resolve) {
                            var infos = [{
                                    kind: 'audioinput',
                                    deviceId: 'default',
                                    label: '',
                                    groupId: ''
                                },
                                {
                                    kind: 'videoinput',
                                    deviceId: 'default',
                                    label: '',
                                    groupId: ''
                                }
                            ];
                            resolve(infos);
                        });
                    };

                if (browserDetails.version < 41) {
                    // Work around http://bugzil.la/1169665
                    var orgEnumerateDevices =
                        navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices);
                    navigator.mediaDevices.enumerateDevices = function() {
                        return orgEnumerateDevices().then(undefined, function(e) {
                            if (e.name === 'NotFoundError') {
                                return [];
                            }
                            throw e;
                        });
                    };
                }
                if (browserDetails.version < 49) {
                    var origGetUserMedia = navigator.mediaDevices.getUserMedia.
                    bind(navigator.mediaDevices);
                    navigator.mediaDevices.getUserMedia = function(c) {
                        return origGetUserMedia(c).then(function(stream) {
                            // Work around https://bugzil.la/802326
                            if (c.audio && !stream.getAudioTracks().length ||
                                c.video && !stream.getVideoTracks().length) {
                                stream.getTracks().forEach(function(track) {
                                    track.stop();
                                });
                                throw new DOMException('The object can not be found here.',
                                    'NotFoundError');
                            }
                            return stream;
                        }, function(e) {
                            return Promise.reject(shimError_(e));
                        });
                    };
                }
                if (!(browserDetails.version > 55 &&
                        'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
                    var remap = function(obj, a, b) {
                        if (a in obj && !(b in obj)) {
                            obj[b] = obj[a];
                            delete obj[a];
                        }
                    };

                    var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.
                    bind(navigator.mediaDevices);
                    navigator.mediaDevices.getUserMedia = function(c) {
                        if (typeof c === 'object' && typeof c.audio === 'object') {
                            c = JSON.parse(JSON.stringify(c));
                            remap(c.audio, 'autoGainControl', 'mozAutoGainControl');
                            remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression');
                        }
                        return nativeGetUserMedia(c);
                    };

                    if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
                        var nativeGetSettings = MediaStreamTrack.prototype.getSettings;
                        MediaStreamTrack.prototype.getSettings = function() {
                            var obj = nativeGetSettings.apply(this, arguments);
                            remap(obj, 'mozAutoGainControl', 'autoGainControl');
                            remap(obj, 'mozNoiseSuppression', 'noiseSuppression');
                            return obj;
                        };
                    }

                    if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
                        var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints;
                        MediaStreamTrack.prototype.applyConstraints = function(c) {
                            if (this.kind === 'audio' && typeof c === 'object') {
                                c = JSON.parse(JSON.stringify(c));
                                remap(c, 'autoGainControl', 'mozAutoGainControl');
                                remap(c, 'noiseSuppression', 'mozNoiseSuppression');
                            }
                            return nativeApplyConstraints.apply(this, [c]);
                        };
                    }
                }
                navigator.getUserMedia = function(constraints, onSuccess, onError) {
                    if (browserDetails.version < 44) {
                        return getUserMedia_(constraints, onSuccess, onError);
                    }
                    // Replace Firefox 44+'s deprecation warning with unprefixed version.
                    utils.deprecated('navigator.getUserMedia',
                        'navigator.mediaDevices.getUserMedia');
                    navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
                };
            };

        }, {
            "../utils": 13
        }],
        12: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            'use strict';
            var utils = require('../utils');

            module.exports = {
                shimLocalStreamsAPI: function(window) {
                    if (typeof window !== 'object' || !window.RTCPeerConnection) {
                        return;
                    }
                    if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
                        window.RTCPeerConnection.prototype.getLocalStreams = function() {
                            if (!this._localStreams) {
                                this._localStreams = [];
                            }
                            return this._localStreams;
                        };
                    }
                    if (!('getStreamById' in window.RTCPeerConnection.prototype)) {
                        window.RTCPeerConnection.prototype.getStreamById = function(id) {
                            var result = null;
                            if (this._localStreams) {
                                this._localStreams.forEach(function(stream) {
                                    if (stream.id === id) {
                                        result = stream;
                                    }
                                });
                            }
                            if (this._remoteStreams) {
                                this._remoteStreams.forEach(function(stream) {
                                    if (stream.id === id) {
                                        result = stream;
                                    }
                                });
                            }
                            return result;
                        };
                    }
                    if (!('addStream' in window.RTCPeerConnection.prototype)) {
                        var _addTrack = window.RTCPeerConnection.prototype.addTrack;
                        window.RTCPeerConnection.prototype.addStream = function(stream) {
                            if (!this._localStreams) {
                                this._localStreams = [];
                            }
                            if (this._localStreams.indexOf(stream) === -1) {
                                this._localStreams.push(stream);
                            }
                            var pc = this;
                            stream.getTracks().forEach(function(track) {
                                _addTrack.call(pc, track, stream);
                            });
                        };

                        window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                            if (stream) {
                                if (!this._localStreams) {
                                    this._localStreams = [stream];
                                } else if (this._localStreams.indexOf(stream) === -1) {
                                    this._localStreams.push(stream);
                                }
                            }
                            return _addTrack.call(this, track, stream);
                        };
                    }
                    if (!('removeStream' in window.RTCPeerConnection.prototype)) {
                        window.RTCPeerConnection.prototype.removeStream = function(stream) {
                            if (!this._localStreams) {
                                this._localStreams = [];
                            }
                            var index = this._localStreams.indexOf(stream);
                            if (index === -1) {
                                return;
                            }
                            this._localStreams.splice(index, 1);
                            var pc = this;
                            var tracks = stream.getTracks();
                            this.getSenders().forEach(function(sender) {
                                if (tracks.indexOf(sender.track) !== -1) {
                                    pc.removeTrack(sender);
                                }
                            });
                        };
                    }
                },
                shimRemoteStreamsAPI: function(window) {
                    if (typeof window !== 'object' || !window.RTCPeerConnection) {
                        return;
                    }
                    if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
                        window.RTCPeerConnection.prototype.getRemoteStreams = function() {
                            return this._remoteStreams ? this._remoteStreams : [];
                        };
                    }
                    if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
                        Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
                            get: function() {
                                return this._onaddstream;
                            },
                            set: function(f) {
                                var pc = this;
                                if (this._onaddstream) {
                                    this.removeEventListener('addstream', this._onaddstream);
                                    this.removeEventListener('track', this._onaddstreampoly);
                                }
                                this.addEventListener('addstream', this._onaddstream = f);
                                this.addEventListener('track', this._onaddstreampoly = function(e) {
                                    e.streams.forEach(function(stream) {
                                        if (!pc._remoteStreams) {
                                            pc._remoteStreams = [];
                                        }
                                        if (pc._remoteStreams.indexOf(stream) >= 0) {
                                            return;
                                        }
                                        pc._remoteStreams.push(stream);
                                        var event = new Event('addstream');
                                        event.stream = stream;
                                        pc.dispatchEvent(event);
                                    });
                                });
                            }
                        });
                    }
                },
                shimCallbacksAPI: function(window) {
                    if (typeof window !== 'object' || !window.RTCPeerConnection) {
                        return;
                    }
                    var prototype = window.RTCPeerConnection.prototype;
                    var createOffer = prototype.createOffer;
                    var createAnswer = prototype.createAnswer;
                    var setLocalDescription = prototype.setLocalDescription;
                    var setRemoteDescription = prototype.setRemoteDescription;
                    var addIceCandidate = prototype.addIceCandidate;

                    prototype.createOffer = function(successCallback, failureCallback) {
                        var options = (arguments.length >= 2) ? arguments[2] : arguments[0];
                        var promise = createOffer.apply(this, [options]);
                        if (!failureCallback) {
                            return promise;
                        }
                        promise.then(successCallback, failureCallback);
                        return Promise.resolve();
                    };

                    prototype.createAnswer = function(successCallback, failureCallback) {
                        var options = (arguments.length >= 2) ? arguments[2] : arguments[0];
                        var promise = createAnswer.apply(this, [options]);
                        if (!failureCallback) {
                            return promise;
                        }
                        promise.then(successCallback, failureCallback);
                        return Promise.resolve();
                    };

                    var withCallback = function(description, successCallback, failureCallback) {
                        var promise = setLocalDescription.apply(this, [description]);
                        if (!failureCallback) {
                            return promise;
                        }
                        promise.then(successCallback, failureCallback);
                        return Promise.resolve();
                    };
                    prototype.setLocalDescription = withCallback;

                    withCallback = function(description, successCallback, failureCallback) {
                        var promise = setRemoteDescription.apply(this, [description]);
                        if (!failureCallback) {
                            return promise;
                        }
                        promise.then(successCallback, failureCallback);
                        return Promise.resolve();
                    };
                    prototype.setRemoteDescription = withCallback;

                    withCallback = function(candidate, successCallback, failureCallback) {
                        var promise = addIceCandidate.apply(this, [candidate]);
                        if (!failureCallback) {
                            return promise;
                        }
                        promise.then(successCallback, failureCallback);
                        return Promise.resolve();
                    };
                    prototype.addIceCandidate = withCallback;
                },
                shimGetUserMedia: function(window) {
                    var navigator = window && window.navigator;

                    if (!navigator.getUserMedia) {
                        if (navigator.webkitGetUserMedia) {
                            navigator.getUserMedia = navigator.webkitGetUserMedia.bind(navigator);
                        } else if (navigator.mediaDevices &&
                            navigator.mediaDevices.getUserMedia) {
                            navigator.getUserMedia = function(constraints, cb, errcb) {
                                navigator.mediaDevices.getUserMedia(constraints)
                                    .then(cb, errcb);
                            }.bind(navigator);
                        }
                    }
                },
                shimRTCIceServerUrls: function(window) {
                    // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
                    var OrigPeerConnection = window.RTCPeerConnection;
                    window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                        if (pcConfig && pcConfig.iceServers) {
                            var newIceServers = [];
                            for (var i = 0; i < pcConfig.iceServers.length; i++) {
                                var server = pcConfig.iceServers[i];
                                if (!server.hasOwnProperty('urls') &&
                                    server.hasOwnProperty('url')) {
                                    utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                                    server = JSON.parse(JSON.stringify(server));
                                    server.urls = server.url;
                                    delete server.url;
                                    newIceServers.push(server);
                                } else {
                                    newIceServers.push(pcConfig.iceServers[i]);
                                }
                            }
                            pcConfig.iceServers = newIceServers;
                        }
                        return new OrigPeerConnection(pcConfig, pcConstraints);
                    };
                    window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
                    // wrap static methods. Currently just generateCertificate.
                    if ('generateCertificate' in window.RTCPeerConnection) {
                        Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                            get: function() {
                                return OrigPeerConnection.generateCertificate;
                            }
                        });
                    }
                },
                shimTrackEventTransceiver: function(window) {
                    // Add event.transceiver member over deprecated event.receiver
                    if (typeof window === 'object' && window.RTCPeerConnection &&
                        ('receiver' in window.RTCTrackEvent.prototype) &&
                        // can't check 'transceiver' in window.RTCTrackEvent.prototype, as it is
                        // defined for some reason even when window.RTCTransceiver is not.
                        !window.RTCTransceiver) {
                        Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
                            get: function() {
                                return {
                                    receiver: this.receiver
                                };
                            }
                        });
                    }
                },

                shimCreateOfferLegacy: function(window) {
                    var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
                    window.RTCPeerConnection.prototype.createOffer = function(offerOptions) {
                        var pc = this;
                        if (offerOptions) {
                            if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
                                // support bit values
                                offerOptions.offerToReceiveAudio = !!offerOptions.offerToReceiveAudio;
                            }
                            var audioTransceiver = pc.getTransceivers().find(function(transceiver) {
                                return transceiver.sender.track &&
                                    transceiver.sender.track.kind === 'audio';
                            });
                            if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
                                if (audioTransceiver.direction === 'sendrecv') {
                                    if (audioTransceiver.setDirection) {
                                        audioTransceiver.setDirection('sendonly');
                                    } else {
                                        audioTransceiver.direction = 'sendonly';
                                    }
                                } else if (audioTransceiver.direction === 'recvonly') {
                                    if (audioTransceiver.setDirection) {
                                        audioTransceiver.setDirection('inactive');
                                    } else {
                                        audioTransceiver.direction = 'inactive';
                                    }
                                }
                            } else if (offerOptions.offerToReceiveAudio === true &&
                                !audioTransceiver) {
                                pc.addTransceiver('audio');
                            }


                            if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
                                // support bit values
                                offerOptions.offerToReceiveVideo = !!offerOptions.offerToReceiveVideo;
                            }
                            var videoTransceiver = pc.getTransceivers().find(function(transceiver) {
                                return transceiver.sender.track &&
                                    transceiver.sender.track.kind === 'video';
                            });
                            if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
                                if (videoTransceiver.direction === 'sendrecv') {
                                    videoTransceiver.setDirection('sendonly');
                                } else if (videoTransceiver.direction === 'recvonly') {
                                    videoTransceiver.setDirection('inactive');
                                }
                            } else if (offerOptions.offerToReceiveVideo === true &&
                                !videoTransceiver) {
                                pc.addTransceiver('video');
                            }
                        }
                        return origCreateOffer.apply(pc, arguments);
                    };
                }
            };

        }, {
            "../utils": 13
        }],
        13: [function(require, module, exports) {
            /*
             *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
             *
             *  Use of this source code is governed by a BSD-style license
             *  that can be found in the LICENSE file in the root of the source
             *  tree.
             */
            /* eslint-env node */
            'use strict';

            var logDisabled_ = true;
            var deprecationWarnings_ = true;

            /**
             * Extract browser version out of the provided user agent string.
             *
             * @param {!string} uastring userAgent string.
             * @param {!string} expr Regular expression used as match criteria.
             * @param {!number} pos position in the version string to be returned.
             * @return {!number} browser version.
             */
            function extractVersion(uastring, expr, pos) {
                var match = uastring.match(expr);
                return match && match.length >= pos && parseInt(match[pos], 10);
            }

            // Wraps the peerconnection event eventNameToWrap in a function
            // which returns the modified event object.
            function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
                if (!window.RTCPeerConnection) {
                    return;
                }
                var proto = window.RTCPeerConnection.prototype;
                var nativeAddEventListener = proto.addEventListener;
                proto.addEventListener = function(nativeEventName, cb) {
                    if (nativeEventName !== eventNameToWrap) {
                        return nativeAddEventListener.apply(this, arguments);
                    }
                    var wrappedCallback = function(e) {
                        cb(wrapper(e));
                    };
                    this._eventMap = this._eventMap || {};
                    this._eventMap[cb] = wrappedCallback;
                    return nativeAddEventListener.apply(this, [nativeEventName,
                        wrappedCallback
                    ]);
                };

                var nativeRemoveEventListener = proto.removeEventListener;
                proto.removeEventListener = function(nativeEventName, cb) {
                    if (nativeEventName !== eventNameToWrap || !this._eventMap ||
                        !this._eventMap[cb]) {
                        return nativeRemoveEventListener.apply(this, arguments);
                    }
                    var unwrappedCb = this._eventMap[cb];
                    delete this._eventMap[cb];
                    return nativeRemoveEventListener.apply(this, [nativeEventName,
                        unwrappedCb
                    ]);
                };

                Object.defineProperty(proto, 'on' + eventNameToWrap, {
                    get: function() {
                        return this['_on' + eventNameToWrap];
                    },
                    set: function(cb) {
                        if (this['_on' + eventNameToWrap]) {
                            this.removeEventListener(eventNameToWrap,
                                this['_on' + eventNameToWrap]);
                            delete this['_on' + eventNameToWrap];
                        }
                        if (cb) {
                            this.addEventListener(eventNameToWrap,
                                this['_on' + eventNameToWrap] = cb);
                        }
                    }
                });
            }

            // Utility methods.
            module.exports = {
                extractVersion: extractVersion,
                wrapPeerConnectionEvent: wrapPeerConnectionEvent,
                disableLog: function(bool) {
                    if (typeof bool !== 'boolean') {
                        return new Error('Argument type: ' + typeof bool +
                            '. Please use a boolean.');
                    }
                    logDisabled_ = bool;
                    return (bool) ? 'adapter.js logging disabled' :
                        'adapter.js logging enabled';
                },

                /**
                 * Disable or enable deprecation warnings
                 * @param {!boolean} bool set to true to disable warnings.
                 */
                disableWarnings: function(bool) {
                    if (typeof bool !== 'boolean') {
                        return new Error('Argument type: ' + typeof bool +
                            '. Please use a boolean.');
                    }
                    deprecationWarnings_ = !bool;
                    return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
                },

                log: function() {
                    if (typeof window === 'object') {
                        if (logDisabled_) {
                            return;
                        }
                        if (typeof console !== 'undefined' && typeof console.log === 'function') {
                            console.log.apply(console, arguments);
                        }
                    }
                },

                /**
                 * Shows a deprecation warning suggesting the modern and spec-compatible API.
                 */
                deprecated: function(oldMethod, newMethod) {
                    if (!deprecationWarnings_) {
                        return;
                    }
                    console.warn(oldMethod + ' is deprecated, please use ' + newMethod +
                        ' instead.');
                },

                /**
                 * Browser detector.
                 *
                 * @return {object} result containing browser and version
                 *     properties.
                 */
                detectBrowser: function(window) {
                    var navigator = window && window.navigator;

                    // Returned result object.
                    var result = {};
                    result.browser = null;
                    result.version = null;

                    // Fail early if it's not a browser
                    if (typeof window === 'undefined' || !window.navigator) {
                        result.browser = 'Not a browser.';
                        return result;
                    }

                    if (navigator.mozGetUserMedia) { // Firefox.
                        result.browser = 'firefox';
                        result.version = extractVersion(navigator.userAgent,
                            /Firefox\/(\d+)\./, 1);
                    } else if (navigator.webkitGetUserMedia) {
                        // Chrome, Chromium, Webview, Opera.
                        // Version matches Chrome/WebRTC version.
                        result.browser = 'chrome';
                        result.version = extractVersion(navigator.userAgent,
                            /Chrom(e|ium)\/(\d+)\./, 2);
                    } else if (navigator.mediaDevices &&
                        navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) { // Edge.
                        result.browser = 'edge';
                        result.version = extractVersion(navigator.userAgent,
                            /Edge\/(\d+).(\d+)$/, 2);
                    } else if (window.RTCPeerConnection &&
                        navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) { // Safari.
                        result.browser = 'safari';
                        result.version = extractVersion(navigator.userAgent,
                            /AppleWebKit\/(\d+)\./, 1);
                    } else { // Default fallthrough: not supported.
                        result.browser = 'Not a supported browser.';
                        return result;
                    }

                    return result;
                }
            };

        }, {}]
    }, {}, [3])(3)
});
